Title of Invention	DIPHOSPHINES, PREPARATION THEREOF
Abstract	The invention concerns novel diphosphines of formula (I) useful in particular, in their optically active form, as ligands in metal complexes. The invention also concerns their uses an intermediates in the preparation of polymeric insoluble ligands. The invention further concerns the use of said insoluble ligafldsin the preparation of metal complexes for asymmetric catalysis.

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DIPHOSPHINES, PREPARATION AND USES THEREOF The present invention relates to novel diphosphines especially in their optically active form, and also to the process for obtaining them. The invention is also directed toward their uses as bidentate ligands in the synthesis of transition metal-based catalysts for asymmetric catalysis. The invention is also directed toward their uses as intermediate products in the preparation of ligands in insoluble form. More particularly, the invention lies in an optically active polymer in which one of the polymer units consists of a chiral diphosphine. • The invention is also directed toward the use of said polymer as " a ligand in the preparation of metal complexes for asymmetric catalysis. The production of pure optically active compounds is a problem that arises in many technical fields, for instance pharmacy, agrochemistry, the food industry (food additives and flavorings) and also in the fragrance industry. This problem is expected to become increasingly important since it has been found more and more that, in a given application, only one of the stereoisomers has the desired property. Asymmetric catalysis has undergone considerable expansion in - recent years. It has the advantage of leading directly to the preparation of optically pure or optically enriched isomers by asymmetric induction without it being necessary to perform resolution of racemic mixtures. 2, 2' -Bis (diphenylphosphino) -1,1' -binaphthyl (BINAP) is an example of a diphosphorus • Mgand commonly used for the preparation of metal complexes for the asymmetric catalysis of hydrogenation, carbonylation, hydrosilyla-tion and C-C bond forming reactions (such as allylic substitutions or Grignard cross-couplings) or even asymmetric isomerization reactions of allylamines. The complexes used are derivatives of palladium, ruthenium, rhodium and iridium salts. The development of novel chiral ligands is desirable for several reasons. Ligands that are capable of improving the enantio-selectivity of reactions are sought. There is also a need for ligands that are industrially readily accessible. Thus, document WO 00/49028 describes a diphosphine ' that is a BINAP derivative, the two naphthyl groups of which bear a substitution in position 6 and 6' . The agenr more specifically concerned is 6,6'-diaminomethylBINAP. However, the preparation of this phosphine is nor readily achievable industrially, since it includes numerous steps: In the pursuit of its research, the Applicant has found-that it is possible to prepare diphosphines that may be prepared much more readily on an industrial scale since they are derived from a commercial product, namely 2,2'-bis (diphenylphosphino)-1,1'-binaphthyl or BINAP. A first subject of the invention is diphosphines in which the naphthyl groups are substituted in the 5,5' position. Another subject of the invention is intermediate products that are diphosphines in dioxide form containing substituents in the 5,5' position. The invention is directed not only toward the racemic mixture but also toward the optically active forms of said diphosphines. Other subjects of the invention are the processes for preparing said disphosphines, and the uses thereof in asymmetric catalysis. The present invention thus provides a diphosphine that may be used as ligands in chiral catalysts, and corresponding to formula (I): in said formula: - Rx and R2, which may be identical or different, represent a hydrogen atom or a substituent, - Ari and Ar*- independently represent an alkyl, alkenyl, cycloalkyl, aryl or arylalkyl group, - Xi and X2, which may be identical or different, represent: a group R, alkyl, alkenyl, alkynyl, cycloalkyl, aryl or arylalkyl, , an alkyl group substituted with one or more halogen atoms, preferably fluorine, or with nitro or amino groups, a halogen atom chosen from bromine, chlorine and iodine, . an -OH group, . a group -C-Rs, . a group -0-CORa, . a group -S-Ra, a -CN group,, . a group derived from the nizrile group such as: . a -CH2-NK? group, . a -COOH arcuo, a group derived from the carboxylic group such as: a group -CCORa/ . a -CH2OH group, -. a group -CC-NH-Rb, . a group derived from the aminomethyl group such as : . a group -CK:-NH-CQ-Rb/ . a group -CH:-NH-CO-NH-Rb, . a group -CH:-N=CH-Ra, . a -CH2-N=C=0 group, . a -CH2-NH44" group, a group comprising a nitrogen atom such as: . a group -NHRa, . a group -N(Ra)2, . a group -N=CH-Ra, . an -NH-NH2 group, • an -N=N+=N~ group, . an -N=C=0 group, . a magnesium or lithium atom, in the various formulae, Ra represents an alkyl, cycloalkyl, arylalkyl or phenyl group and Rb has the meaning given for Ra and also represents a naphthyl group. The present invention is also directed toward "he intermediate products, i.e. the diphosphine in dioxide form, in racer-ic form or in chiral form, and which corresponds to the following formula: in said formula (II) , Ri, R2, Ar:/ Ar2, Xi and X2 have the meaning given for formula (I) . Among the diphosphines corresponding to the general formula (I), one particularly advantageous group of diphosphines is that consisting of the diphosphines corresponding to formula (I' ) , which may be used as intermediate products for the preparation of .insoluble polymers as constituents of one of -he polymer units: in said formula: - R: and R2, which may .be identical or different, represent a hydrogen atom :r a substituent, - Ari and Ar: independently represent an alkyl, alkenyl, cycloalkyl, aryl cr arylalkyl group, - Xi and X2, which are identical, represent: . an -OK group, . a -CH?OK crouc, a -CK?-Nr^2;• a group -C30Ra in which Ra represents an aikyl, cycloaikyi, arylalkyl or phenyl group, an -N=C~0 group, . a -CH2-N=C=0 group. The characteristic of the diphosphines of formula {!'} is that they bear two functional groups capable of ^ . reacting with one or more pclymerizable monomers leading to a polymer which, when it is obtained from a chiral diphosphine, is optically active and, is thus able to be used as a ligand in metal complexes used in asymmetric catalysis. The definition of certain terms used ~in the present text is recalled hereinbelow. The term "chiral" refers to a molecular species that is not superposable on its mirror image. A compound is racemic if it is the equimolar mixture of its two enantiomeric forms. The term "enantiomers" denotes molecular species that are mirror images of each other and that are not superposable. A compound is optically active if it is capable of rotating the plane of polarization of a transmitted beam of plane polarized light. An optically active compound is necessarily chiral. In the context of the invention, the term "allcyl" means a linear or branched hydrocarbon-based chain containing from 1 to 15 carbon atoms and preferably 1 or 2 to 10 carbon atoms. Examples of preferred alkyl groups are especially methyl, ethyl, propyl, isopropyl, butyl, isobutyl and t-butyl. The term "alkenyl" means a linear or branched hydrocarbon-based group containing from 2 to 15 carbon atoms, comprising one or more double bonds and preferably one or two double bonds. The term xvalkynyl" means a linear or branched hydrocarbon-based group containing from 2 to 15 carbon atoms, comprising one or more triple bonds and preferably one triple bond. The term x>cycloalkyi" means a cyclic hydrocarbon-based group, which is monocyclic comprising from 3 to 8 carbon atoms, preferably a cyclopentyl or cyclohexyi group, or polycyclic (bicyclic or tricyclic) comprising from 4 to 18 carbon atoms, especially a'damantyl or norbornyl. The term "aryl" 'means a monocyclic or polycyclic," preferably monocyclic or bicyclic, aromatic group comprising from 6 to 2 0 carbon atoms, preferably phenyl or naphthyl. When the group is polycyclic, i.e. when it comprises more than one cyclic nucleus, the cyclic nuclei may be fused in pairs or attached in pairs via a bonds. Examples of (C^-C^)aryl groups are especially phenyl, naphthyl, ar.chryl and phenanthryi . The term "arylalkyl" means a linear or branched hydrocarbon-based group bearing a monocyclic aromatic ring and comprising from " tc 12 carbon atoms, preferably benzyl. In formula (I), (Z') or (II), the carbocyclic groups Ar: and Ar2 may bear sucstituents which are' such that they do not interfere with the complexacicn of the ligand tc the metal during the preparation cf the catalyst. Examples of sucstituents are alkyl, alkoxy, thioalkoxy, alkoxyalkyl, thioalkoxyalkyl, pclyoxyalkylene, -SO3K, -3O3M in which M is^an ammonium or metal cation, -PC3H?, -PO3HM or -PO3M: groups in which M is as defined above. Preferably, M is an alkali metal cation such as Na, Li or K. It is desirable for the substituents not to interfere with the reactions performed in'"the preparation of the compounds (I) and (I') starting with the precursors from which they are derived. However, protection and deprotection steps may be envisioned, where appropriate. A person skilled in the art may refer to the following publication Protective Groups in Organic Synthesis, Greene T.W. and Wuts P.G.M., published by John Wiley and Sons, 1991, to perform the protection of particular organic functions. In the alkyl, alkoxy, thioalkoxy, alkoxyalkyl and thio-alkoxyalkyl groups, the alkyl portions are linear or branched saturated hydrocarbon-based groups comprising especially up to 25 carbon atoms, for example from 1 to 12 carbon atoms and better still from 1 to 6 carbon atoms. Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, neopentyl, 2-methylbutyl, 1-ethylpropyl, hexyl, iso-hexyl, neohexyl, 1-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 1, 3-dimethylbutyl, 2-ethylbutyl, 1-methyl-1-ethylpropyl, heptyl, 1-methylhexyl, 1-propylbutyl, 4,4-dimethylpentyl, octyl, 1-methyl-heptyl, 2-ethylhexyl, 5,5-dimethylhexyl, nonyl, decyl, 1-methylnonyl, 3, 7-dimethyloctyl and 7, 7-dimethyloctyl groups. Preferably, the substituents are alkyl or alkoxy groups preferably containing from 1 to 6 carbon atoms. In accordance with the present invention, the preferred ligands and the intermediates thereof correspond, respectively, to formula (I), (I') or (II) in which Ari and Ar2 independently represent a (Ci-C6)alkyl group; a phenyl group optionally substituted with one or more (Ci-C6) alkyl or (C:-C€) alkoxy groups; or a {C^-C^) cyclo-alkyl group optionally substituted with one or more (Ci-Ce) alkyl groups. Among the preferred compounds of formula (I), (I') or (II) are those for which Ari and Ar: are, independently, a (C1-C4)alkyl group; a phenyl group optionally substituted with methyl or tert-butyl; or a (C5-Ce)cycloalkyl group optionally substituted with methyl or tert-butyl. The' compounds of formula (I), (I') or (II) in which Ar: and Ar2 are identical and preferably represent a phenyl group are most particularly preferred. The carbocyclic groups Ar: and Ar2 may bear substituents which are such that they do not interfere with the reactions used in the process of the invention. These substituents are inert under the conditions used in the halogenation (step i) , cyanation (step ii) and reduction (steps iii and iv; reactions. Thus, the invention does not exclude the presence of substituents other chan R: and R2. The naphthyl groups may also bear a substituent represented by R: cr R:, which may be of the same nature as those that have just been mentioned. Preferably, the substituents are alkyl or alkoxy groups preferably containing from 1 to 6 carbon atoms. In formulae (I) , (I' ) and (II) , Rx and R2 preferably represent a hydrogen atom or one or more groups chosen from (C1-C4) alkyl and (Cx-C4) alkoxy. The preferred compounds (I), (I') and (II) do not bear a substituent, which means that Ri and R2 represent a hydrogen atom. As regards the preferred groups Xi and X2, Ra represents an alkyl group containing from 1 to 4 carbon atoms, a cyclohexyl group, a phenyl group and a benzyl group, and Rb has the meaning given for Ra and also represents a naphthyl group. The preferred functional groups located in position 5 and 5' in the compounds of formulae (I) , (I' ) and (II) are the following: . a halogen atom, preferably a bromine or chlorine - -atom, . an alkyl group substituted with one or more fluorine atoms, a -CN group, a -CH2-NH2 group, . a -COOH group. Among the compounds of formula (I) that are especially distinguished are the compounds having the following formula: in said formula: - X represents a chlorine, bromine or iodine atom, - R:, R?, Ar: and Ar2 have the meaning given above. A first sub jeer cf the invention lies in a process for preparing the diphesphine of formula (Iai) , characterized in that it comprises the following steps: i) performing rhe halogenation in "he 5,5' position of a compound of formula (III): in said formula: - R:, R2/ Ari and Ar: have the meaning given above, using a halogen and in the presence of iron, so as re obtain the corresponding dihalo compound of formula: in said formula: - - - X represents a chlorine, bromine or iodine atom, - Rif R2/ Arx and Ar2 have the meaning given above; ii) performing the reduction of the diphosphine in dioxide and dihalo form in position 5,5' of formula (Ilai), into the diphosphine of formula (la:): in said formula: - X represents a chlorine, bromine or iodine atom, - Ri, R2, Ari and Ar2 have the meaning given above. The diphosphine in dioxide form of formula (ill) is known. It may be obtained by oxidation of the diphosphine of formula (IV) : in said formula: - Ri/ R2/ Ari anc* Ar2 have the meaning given above. The diphosphine in oxide form of formula (III) is obtained by oxidation using an agent for oxidizing the diphosphine of formula (IV). Although any type of oxidizing agent may be used, a chemical oxidizing agent, for example potassium permanganate or alternatively molecular oxygen or a gas -containing it, use is preferably made of hydrogen peroxide, preferably in the form_ of an aqueous solution. The concentration of the hydrogen-peroxide solution is advantageously between 10% and 25% by weight. The amount of oxidizing agent used may vary widely from the stoichiometric amount up tc a 100% excess relative to the stoichiometry. An organic solvent that dissolves the diphosphine is used. The solvent may be chosen from aliphatic, cyclcaliphatic and aromatic hydrocarbons, which may or may not be chlorinated. Examples that may be mentioned include di chl or orr.e thane, chloroform, carbon tetrachloride and 1,2-dichloroethane. The concentration cf diphosphine in the reaction solvent is preferably between 0.1 and 50 g/I. The diphosphine, generally dissolved in an adequate solvent, is thus placed in contact with the oxidizing agent. The reaction is advantageously performed at re on temperature, usually between -5°C and 25°C. The reaction time is generally between 30 minutes and 6 hours. The diphosphine is recovered in dioxide form in the organic phase. The aqueous and organic phases are separated. A standard work-up of the phases is performed. Thus, the organic phase is washed with sodium bisulfite, which removes from the aqueous phase the unreacted excess oxidizing agent (peroxide). A common drying operation is preferably performed, over a drying agent, for example sodium sulfate or magnesium sulfate. A diphosphine in dioxide form corresponding to formula (III) and denoted in the text hereinbelow as "diphosphine (PO)" is obtained. In accordance with the present"invention, the halogena-tion reaction of the naphthyl nucleus is performed, which is an electrophilic reaction performed via the action of a halogen, chlorine, bromine or iodine, on the diphosphine in dioxide form and in the presence of a catalyst. This reaction may be performed in the presence of an iron-based catalyse. Iron turnings or filings are preferably used. The amount of iron used is such that the ratio between the number of moles of iron and the number of moles of compound of formula (III) ranges between 15 and 30 and more particularly at about 20. According to one preferred embodiment of the invention, the halogenation takes place in an inert aprotic solvent. Said solvent should have a boiling point of greater than 60°C. Chlorinated or brominated halogenated hydrocarbons are most particularly used, preferably chloroform, carbon tetrachloride or 1,2-dichloroethane. A preferred solvent that may be mentioned is 1,2-dichloroethane. Preferably, the molar ratio of the halogenating agent to the diphosphine (PO) ranges between 15 and 30 and preferably at about 20. When the process, is performed in solution, the concentration of the reagents may vary very widely between 0.01 and 10 mcl/1, for example between 0-05 and " 7~^l /l — ILI\^ J~ / _L . The halogenation reaction, preferably the bro~ination, is performed between 20°C and 100°C and advantageously in the absence of light so as to avoid spurious radical reactions. A dihalo diphosphine (PO) corresponding to formula (Ilai) is thus obtained. It is recovered in a conventional manner: neutralization of the excess bromine with sodium disulfide, treatment with a base 'sodium carbonate or sodium hydrogen carbonate;, separation of the aqueous and organic phases and then recovery of the dihalo diphosphine (PC) from the organic solution, which is dried followed by removal of the organic solvent. In step (ii), the phosphorus atom in oxidized form {?0) is reduced to give the diphosphine of formula (lax). In a following step, reduction of the diphosphine in dioxide form is performed. This step consists in subjecting said diphosphine to a reduction performed using a hydrogenosilane. Said hydrogenosilane may be represented by the following formula: HSiRaRpR5 (Fa) in said formula: - Raf Rp and R5, which may be identical or different, represent a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, a phenyl group or a chlorine atom, - at most two of the groups Ra, Rp and R5 represent a hydrogen atom. The preferred reducing agents correspond to formula Td) in which Ra, Rp. and R5 represent a hydrogen atom, a methyl group, a phenyl group or a chlorine atom. Examples of reducing agents that may be mentioned more particularly include: - A1H3, - PhSiH3, - HSiCl3/ - (CH2)2HSiCl, - CH3(HSiCl) - PMHS or polymethylhydrosiloxane. The invention does not exclude any other type of organosilicon compound comprising an SiH group. The amount of reducing agent is usually a large stoichiometric excess. Thus, the ratio between the number of moles of reducing agent .and the number of moles of diphosphine (PO) ranges between 10 and 70. Among the abovementioned reducing agents, a mixture of PhSiH3 (cr PMHS) and of HSiCl3 is used. In this case, the amount of PhSiH3 is such that the ratio between the number of moles of PhSiH3 and of moles of diphosphine (PC: ranges between 50 and 70. As regards the amount of HSiCls, the ratio between the number of moles cf HSiCl3 and the number of moles of diphosphine (PO) ranges between 1C and 4 0. The reduction reaction is performed at a temperature advantageously chosen between 80°C and 130CC. At the end of reaction, the medium is cooled to room temperature and the product is recovered in solid form after evaporation. The product may be washed one or more times using an organic solvent, preferably a halogenated or ncr.-halogenated aliphatic, cyclcaliphatic or aromatic hydrocarbon. Preferred solvents that may be mentioned include pentane, hexane and cyciohexane. A diphosphine corresponding tc formula (lai) 'is obtained. The present invention also provides .the process for obtaining a diphosphine corresponding to formula (Ia2) : in which Ri, R2, Ari and Ar2 are as defined above. The process of the invention for obtaining the diphosphine of formula (Ia2) more specifically comprises the following steps: i) performing the substitution of the two halogen atoms, preferably bromine atoms, with cyano groups by reacting the diphosphine in dioxide and dihalo form in position 5,5' of formula (Ilai) : in said formula: - X, Ri, R2, Ari and Ar2 have the meaning given above, using a suitable nucleophilic reagent so as to obtain the corresponding dicyano compound (IIa2) : in said formula: - Rir R>2r Ari ar.d Ar2 have the meaning given above, ii; performing rhe reduction of "che diphosphine in dioxide and dicyano form in position 5,5' of formula (Ilao) into the diphosphine of formula (Ia2) : in said formula: - R1, R2, Ar1 and Ar2 have the meaning given above. Starting with a diphosphine in dioxide and dihalo form of formula (Ilai), the next step is a cyanation reaction, which is a nucleophilic substitution. The two halogen atoms borne by the naphthyl nuclei are replaced with cyano groups via the action of a suitable nucleophilic agent. To perform this substitution, a person skilled in the art may use any of the methods known in the art. According to one preferred embodiment of the invention, the nucleophilic agent used is copper(I) or (II) cyanide. The molar ratio of the copper cyanide to the compound of formula (Ilai) is preferably greater than 2, advantageously between 2 and 4 and preferably between 2 and 3. The reaction is preferably performed in a solvent. Examples of solvents that may be mentioned include amides such as dimethylformamide, N-methyl-2-pyrrolid- inone and hexamethylphosphorylamide. Dimethyl formamide is markedly preferred. Pyridine is also a suitable solvent. The reaction temperature is advantageously maintained between 50°C and 200°C and preferably between 100°C and 190°C. The concentration of reagents in the reaction medium generally varies between 0.1 and 10 raol/1, for example between 2 and 7 mcl/1. The isolation of the nitrile involves decomposition of the intermediate complex formed and trapping of the excess cyanide. The hydrolysis cf the intermediate complex may be performed either via the action of hydrated iron chloride or via the action of aqueous ethylenediamine. In the first case, the reaction medium is poured into an aqueous 50-r 3% (g/ml) . iron chloride solution containing concentrated hydrochloric acid. The resulting solution is heated to 40-80cC until the complex has completely decompcsed. The medium is then decanted and extracted in a conventional manner. In the second case, the reaction medium is poured into an aqueous ethylenediamine solution (ethylenediamine/-water: 1/5-1/1 (v v) , for example 1/3) and the mixture is then stirred vigorously. The medium is then decanted and extracted in a manner known per se. A person skilled in the art may take inspiration from the studies of L. Friedman et al. published in J. 0. C. 1961, 26, 1522,' t: isolate the nitrile. Starting with the dicyanc diphosphine (PC! of formula (Ilai), the compound of formula :ia:) is obtained by reduction of the diphosphine in dioxide f trrr. as described above. The present invention moreover provides a process for converting the compounds of formula (Ia2) (which contain two cyano functions) into the corresponding diamine-methyl compounds. Thus, according to another of its aspects, the invention relates to a process comprising, in addition to the steps (i) and {ii) defined above for the preparation of the diphosphine of formula (la: j / an additional step of reduction of the nitrile function of-the compound of formula (Ia2) via the action of a reducing agent, so as to obtain a compound of formula (Ia3) : in said formula: - Ri, R2/ Ar-_ and Ar2 have the meaning given above. In a "following step, the reduction of the cyano group is performed. A suitable reducing agent is lithium aluminum hydride (LiAlH4) . The invention is not intended to be limited to the use of this particular reducing age-nt. The reaction is preferably performed in a solvent or a mixture of solvents. When the reducing agent is LiAlK4, the solvent advantageously comprises one or more aromatic hydrocarbons (such as benzene, toluene and xylene) as a mixture with one or more ethers. Ethers that may be mentioned include C-.-Ce alkyl ethers (diethyl ether and diisopropyl ether), cyclic ethers (dicxane or tetrahydrofuran), dimethoxyethane and diethylene glycol dimethyl ether. Cyclic ethers such as tetrahydrofuran are preferred. When the reducing agent is LiAlH4, a mixture of toluene and tetrahydrofuran in proportions ranging between 70-50/30-50: toluene/tetrahydrofuran (for example 60/4 0: toluene/THF) (v/v,1 will more preferably be selected. The reduction may be performed at a temperature of between 20°C and 100°C and preferably-between 40°C and 30CC. A large excess of the reducing agent is usually used. Thus, the molar ratio of the reducing agent to the compound of formula (132) generally ranges between 1 and 30, for example between 2 and 20 and especially between 5 and IS. The concentration of reagents in the medium is variable. It may be. maintained between 0.005 and 1 mol/1. A compound of formula (Ia3) is obtained, which may be recovered in a conventional manner, especially by treatment with a base (sodium hydroxide) to remove one aluminates, followed by filtration, drying and evaporation. The compounds of formula (Ia3) obtained according to one process of the invention are novel and form ancoher subject of the invention. Among these compounds, the ones chat: are preferred are those for which Ar: and Ar2 are chosen from a (C:-C;}-alkyl group from phenyl optionally substituted wioh methyl or tert-butyl; and (C5-C.5: cycioalkyl optionally substituted with meohyl or tert-butyl. The compounds of formula (Ia3) in which Ari and Ar~ are identical and represent a phenyl group are more preferably chosen. As a variant, it is possible to convert the two cyano functions of the compounds of formula (Ia2) into carboxylic acid, imine, hydroxymethyl or amide functions. The products resulting from these conversions are ligands that may also be used in asymmetric catalysis. As a variant, the invention provides a process comprising, in addition to steps (i) and (ii) defined above, the step consisting in treating, in acidic medium* c"r in basic medium, the compound of formula (Ia2) so as to obtain the corresponding carboxylic acid of formula (Ia4): in said formula: - R:, R2, Ari and Ar2 have the meaning given above. The conversion of a nitrile function into a carboxylic acid_ function is described in the standard texts of organic chemistry. Thus, a person skilled in the art can readily determine the appropriate reaction conditions. Cne simple- way of proceeding consists in using aqueous sodium hydroxide as hydrolysis agent. As a variant, it is possible to convert the two carboxylic functions of the compounds of formula (Ia A diphosphine of formula (la;) that corresponds to formula (I) or (I') in which X; and X2 represent a group -CO0R£ is obtained by direct esterification of the compound of formula (Ia4) , performed conventionally in basic medium. A diphosphine of formula (la.-) that corresponds to formula (I) or (I' ) in which X: and X2 represent a ~CH2OH group is obtained by reduction of the compound of formula (la.:; using, for example, LiAlH, [Gaylord, N.G. Raduction with complex metals hydride; Wiley: NY, 1956, p. 322]- A diphosphine cf formula (la-) that corresponds to formula (I) or (I' ) in which X: and X2 represent a group -CO-NH-Rb is obtained by reaction of the compound of formula (la.;) with an amine Rb-NK: in the presence cf a coupling agent, for instance DCC (dicyclohexyl carbamate) -(Klausner Y.S., Bodansky M., Synthesis, 1972, 453) . As a variant, it is possible to convert the two amino-methyl functions of the compounds of formula (Ia3) into amide or urea functions. A diphosphine of formula (Ia8) that corresponds to formula (I) or (I') in which Xi and X2 represent a group -CH2-NH-CO-Rb is obtained by reacting the compound of formula (Ia3) with an acid Rb-COOH in the presence of a coupling agent, for instance DCC (Klausner Y. S. , Bodansky M., Synthesis, 1972, 453). A diphosphine of formula (lag) that corresponds to formula (I) or (I') in which Xi and X2 represent a group -CH2-NH-CO-NH-Rb is obtained by reacting the compound of formula (Ia3) with an isocyanate Rb-NCO generally in solvent medium [Rob Ter Halle, Benoit Colasson, Emanuelle Schulz, Michel Spagnol, Marc Lemaire, Tetrahedron Letters, 2000, (41) 643-646]. A diphosphine of formula (Iaio) that corresponds to formula (I) -or (I') in which Xi and X2 represent a group -CH2-N=:CH-R3 is obtained by reacting the compound of formula (Ia3) with an aldehyde Ra-CH0 (Farrar W.V., fee. Chem. Prog., 1968, 29, 85). A diphcsphine of formula (Ia::) that corresponds to formula (I) or (I') in which Xi and X2 represent a -CH2-N=C=0 group is obtained by reaction of the compound of formula (133) with phosgene, performed according to the reaching of the literature especially by Jerry March, Advanced Organic Chemistry, 5th Edition, John Wiley and Sons, p. 507. A diphosphine of formula (Ia:2) that corresponds to formula (I) or (I' ) in which X: and X2 represent a -CH2-NK4" group is obtained by placing the compound of formula (las) in contact with an acid, preferably hydro- bromic acid, at room temperature, in a suitable solvent capable of dissolving the compound cf formula (Ia3) . A suitable solvent is, for example, an aprotic solvent such as a haloger.ated aliphatic hydrocarbon (such as dichlcromethane or trichloroethylene) or an optionally halogenaoed aromatic hydrocarbon" such as toluene cr haioger.ated toluene. The diphosphine of formula (Ian) is recovered in aqueous phase. liphcsphines of formula (Iai3) cr (Ia^) that correspond 00 formula (I) or (I') in 'which X: and X2 represent, respectively, a group -NHRa or a group -N(Ra) 2 are obtained by reacting, respectively, the diphosphine in dioxide and dihalc form of formula .Hai) and an amine R=NK: or {Ra} 2NH : Ka zankov M. V. , Sinodman L. G. , Organic. Chem., USSR, 1975, 11, 451) followed by reduction cf the diphosphine in dioxide form as H o c r ^ *' ^ n ^ 2 nnvo A diphosphine of formula (Ia:e ] that corresponds to formula (I) or (I' in which Xi and X: represent a group -N=CH-Ra is obtained by reacting ammonia with the diphosphine in dioxide and dihalo form of formula (IIa:! followed by reaction of the amino group with a compound of the type Ra-CHO, followed by reduction of the diphosphine in dioxide form as described above. A diphosphine of formula (Ia:5) that corresponds ~o formula (I) or (I') in which X: and X2 represent an -NH-NH2 group is obtained by reacting hydrazine with che diphosphine in dioxide and dihaio form of formula (IIa:) (Kazankov M.V., Ginodman L.G., J. Org. Cham., USSR, 1975, 11, 4 51) followed by reduction of the diphosphine in dioxide form as described above. A diphosphine of formula (Ia-j) that corresponds ~c* • formula (I) or (I') in which X: and X2 represent an -N=N+=N" group is obtained by reacting HN3 or NaN3 wich the diphosphine in dioxide and dihaio form of formula (Ilai) (Scriven E. F.V., Turnbull K. , Chem. Rev., 1988, 88, 297) followed by reduction of the diphosphine in dioxide form as described above. A diphosphine of formula (Iais) that corresponds ~o formula (I) or (I' ) in which XL and X2 represent an -N=C=0 group is obtained by reacting the compound of formula (Iai3) with phosgene, performed according to the teaching of the literature, especially by Jerry March, Advanced Organic Chemistry, 5th Edition, John Wiley and Sons, p. 507. As a variant, the invention also provides a diphosphine of formula (Iaig) in which Xi and X2 represent a hydrocarbon-based group R chosen from alkyl, alkenyi, alkynyl, cycloalkyl, aryl and arylalkyl groups and which is obtained by preparing the organomagnesium reagent corresponding to the dihaio diphosphine (Ilai) in dioxide form by reacting the latter with magnesium, followed by reaction of the reagent obtained with -he halogenated hydrocarbon R-X0 (X0 = Br or CI) (Kharasch K.S., Reinmuth 0., Grignard reactions of nonmetallic substances; Prentice-Hall: Englewood Cliffs, NJ, 1954, 5)\ A reduction of the diphcsphine in dioxide form is then performed as described above. As a variant, the invention also provides a diphosphine of formula (Ia2o) in which Xi and X2 represent an alkyl group substituted with one or more halogen atoms, especially with fluorine atoms. It is preferably a perfluoroalkyl group of the type -(CH2)pFq in which p is between 1 and 15 and preferably between 6 and 10, and q is between 3 and 21 and preferably between 13 and 25. The production of such a diphosphine is obtained by reacting the diphosphine in dioxide and dihalo form of formula (Ilai) with the corresponding iodo species I(CH2)pFqf p and q having the meanings given above, in the presence cf copper, optionally a base, and a polar — — ~ ,,0^ 4- -Dw-L VtliU . The ratio between the number of moles of diphosphine cf formula (Ilai) and the number cf moles of iodoperfluoro compound ranges between 1 and 5 and preferably between ' P -, ^ ^ The ratio between the number cf moles of copper and the number cf moles of dibromo diphosphine ranges between 5 and 10. As regards the base, use is made cf a trapping base especially such as those mentioned above, in particular bipyridine. The ratio between the number cf moles of base and the number of moles of dibromo diphosphine ranges between .0 .1 and 1. The reaction advantageously takes place in a polar solvent, for instance dimethyl sulfoxide, dimethyl-f ormamide or fiuorobenzene . The reaction takes place between 60°C and 100°C and preferably between ~2'Z and 80°C. The reaction lasts between 24 and 36 hours. At the end of reaction, the mixture is diluted with a solvent (for example dichloromethane), the copper is separated out by -filtration and the organic phase is recovered, which is conventionally washed with water and then with a dilute acid solution (for example IN HCI) and-then with sodium hydrogen carbonate. The organic phase is dried and the solvent is then removed by evaporation. The diphosphine in dioxide form containing perfluoroalkyl groups in positions 5 and 5' is recovered. A reduction of the diphosphine in dioxide form is then performed as described above. As a variant, the invention also provides a diphosphine of formula (Ia21) in which Xx and X2 represent a hydroxyl group. It is obtained from the diphosphine in dioxide and dihalo form of formula (Ilai) , according to an aromatic nucleophilic substitution with OH- [Fyfe, C.A. in Patai The Chemistry of the hydroxyl group, Pt. 1, Wiley: NY, 1971, p. 83]. A reduction of the diphosphine in dioxide form is then performed as described above. The invention also provides a diphosphine of formula (Ia22) in which Xi_ and X2 represent a group -OCORa. It is obtained from the diphosphine of formula (Iai7) by reaction with the carboxylic acid RaCOOH or a derivative (halide or anhydride), according to a standard esterification reaction. The process of the invention may be performed starting with an optically active compound of formula (IV) with conservation of the chirality from the start to the end of the synthesis. Thus, starting with (S)-BINAP, (S)-5,5'-diaminomethyl-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl is obtained. Starting with (R)-BINAP, (R)-b,5'-diamino-methyl-2, 2' -bis(diphenylphosphino)-1,1'-binaphthyl is obtained. According to another aspect of the invention, the invention relates to the use of diphosphine in which the naphthyl groups are substituted in the 5,5' position with two identical functional groups capable of reacting with pclymerizable monomers, leading to a racemic or optically active polymer. The diphosphines used correspond to formula (I'). In formula (I'), Xi represents an aminomethyl group -CK1-NK2, a hydrcxyl group -OH, a hydroxymethyl group -CHi-OH, a carboxylic or ester group -COORa (R£ represents a hydrogen atom or ar. alkyl, cycloalkyl, arylalkyl or phenyl group, more preferably a hydrogen atom or a C1-C2 alkyl group), an isocyanato group -N=C=3 or an isocyanatomethy1 group -CH:-K=C=0. Advantageously, they are diphosphines corresponding to formulae (la-) , ;ia3) , (Ia4) , (Ias) , (Ia6) , (Ian) and (Ia:e) . Another subject of the invention thus lies in optically active polymers comprising the chiral diphosphine of formula (I') as polymer units. Another subject of the invention consists of the use of the optically active polymer as a ligand in the preparation of metal complexes for asymmetric catalysis. The polymer of the invention consists of a sequence of two types of units. The first type of unit is the chiral diphosphine residue corresponding to formula (I' ) and bearing two identical polymerizable functional groups. The second type of unit is a monomer residue that is polymerizable with said functional groups, i.e. a monomer comprising at least two identical functional groups capable of reacting with the functional groups of the chiral diphosphine. The preferred monomer is di functional and may be represented by formula (X) below: in which: - M represents a divalent hydrocarbon-based group of aliphatic, alicyclic and/or aromatic nature, - Yi represents a functional group, preferably a ■'carboxylic, ester, hydroxy!, amino, isocyanato, aldehyde or ketone group. The size of the group M will be adjusted by a person skilled in the art as a function of the final use of "Che ligand and especially as a function of the reaction that the metal complex formed from this polymer ligand is intended to catalyze. Preferred meanings will be given later for the reagents preferentially chosen. It will be pointed out that the monomers most often used correspond to formula (X) in which M represents a C1-C12 and preferably Ci-C6 alkylene chain; a cyclo-alkylene and preferably a cyclohexylene group; an arylene group, preferably phenylene, tolylene or naphthalene• Thus, the optically active polymer resulting from the polymerization of the diphosphine of formula (I') and of the monomer of formula (X) comprises the following repeating unit: in which - R-_ and R-, which may be identical or different, represent a hydrogen atom or a substituent, - Ar: and Ar: independently represent an alkyl, aikenyl, cycioalkyi, aryl or arylaTkyl group, - M represents a divalent hydrocarbon-based group of aliphatic, alicyciic and/or aromatic nature; - Fi represents a functional group resulting from the reaction: . of the group X: chosen from the following groups: aminomethyl, hydroxy1, hydroxymethyl, carboxylie, ester, isocyanato, isocyanatomethyl, . and of the group Y: chosen from carboxylic, ester, hydroxy1, amino, isocyanato, aldehyde and ketone groups, - the degree of polymerization is preferably between 2 and 100 and better still between 2 and 50". The choice of these functions, combined with the choice of the polymerizable monomers, determines the nature of the resulting polymer. Thus, Fi more particularly represents: - a urea group (Ft) resulting from the reaction of an aminomethyl group (Xi) with an isocyanato group (Yi) or an isocyanato or isocyanatomethyl group (Xi) with an amino group (Yi) , - a urethane group (Fi) resulting from the reaction of an isocyanato or isocyanatomethyl group (Xi) with a hydroxy1 group (Y:) or a hydroxy1 or hydroxymethyl group (Xi) with an isocyanato group (Yi), - an ester group (Fi) resulting from the reaction of a carboxylic or ester group (Xi) with a hydroxyl group (Yi) or a hydroxyl or hydroxymethyl group (Xi) with a carboxylic or ester group (Yi) , - an amide group (Fi) resulting from the reaction of a carboxylic group (Xi) with an amino group (Yi) or an aminomethyl group (Xi) with a carboxylic group (Yx), - an imine group (Fi) resulting from the reaction of an aminomethyl group (Xi) with an aldehyde or ketone -group (Yi) . The present invention encompasses all types of polymers and especially linear, branched or crosslinked polymers. Mention may be made of polymers such as polyester, polyurethane, polyamide, polyurea, polyimine and polyimide. The preferred polymers are linear polymers, but the invention does not exclude crosslinked polymers obtained by using a polymerizable monomer comprising more than two functional groups, for example three groups. The choice of monomers placed in contact will be made as a function of their ease of access. Thus, the invention favors the chiral substance bearing in position 5,5' two aminomethyl groups. The compounds preferably used, corresponding to formula (la; \ in which Ar: and Ar2 are independently chosen from a 'Zi-Ci)alkyl croup or a phenyl group optionally substituted with methyl or tert-butyl; and (C5-Ce; -cycloalkyl optionally substituted with methyl or tert- Those of formula (Ia^) in which Ari and Ar2 are identical and represent a phenyl group are more preferably chosen. In accordance with the invention, one of the diphos-phines corresponding to one of the formulae (I') is reacted with a polymerizable monomer. It is preferentially ■ chosen to use only one polymerizable monomer. Classes of monomers that may esceciaxxy u~ nicu.i'juc-include diacids, diesters, diols, diisocyanates, dialdehydes and diketones. Although the invention is not intended to be specifically limited thereto, polyamides, pclyureas and polyimides will be described in further detail. The polyureas, polyamides and polyimides of the invention may be prepared starting with a chiral diphosphine* consisting of a chiral substance bearing, as functional groups, two aminomechyl groups, and which corresponds to the formulae (Ia3). Polyureas When the targeted polymer is a polyurea, it may be synthesized by polymerization of a diphosphine bearing two -CH2-NH2 groups with one or more di- or poiyisc- cyanates. The nature of the isocyanate compound is not critical per se. Preferably, the diisocyanate is a diisocyanate of formula (Xa): 0=C=N-J-N=C=0 (Xa) in which: . - - J represents a divalent hydrocarbon-based group of aliphatic, alicyclic and/or aromatic nature. The size of the group J will be adjusted by a person skilled in the art as a function of the final use of the ligand and especially as a function of the reaction that the metal complex formed from this polymer ligand is intended to catalyze. The catalytic sites of the polymer of the invention are located on the diphosphine-based units. The size of the group J thus determines the spacing of" the catalytic sites. The group J is, for example, a Ci-Cie and preferably Ci-C12 alkylene chain, optionally interrupted with one or more (preferably 1 to 4 and better still 1 to 2) hetero atoms chosen from 0, N and S, said chain optionally comprising one cr mere unsaturations (preferably 1 to 4 and better still 1 to 2); a croup - (CH2) &-K- (CH2) b~ in which a and b are, independently, an integer from 0 to 6 and K represents (C£-Ce) cyclcalkylene; a group - (CK2) a~L~ (CH2) t- in which a and b are as defined above and L represents (C6-C;:) arylene; a group - (Cr>) a-Vc- (CH2) ~- in which a and b are as defined above and Vc represents a 5- to S-membered heteroarylene comprising 1 to l hetero atoms chesen from O, N and S; or alternatively a group -Kc-Q-Kz' in which M0 is chosen from (Cs-Ce) cyclcalkylene and (C^-C—) arylene and Q represents a bond, a sulfur atom, an oxygen atom., (C:-CU) alkylene, -SO-, -S0:- or -CO-. When J contains an alkylene chain, it is linear cr branched and preferably contains 1 to 6 carbon atoms. When this alkylene chain comprises a nitrogen atom, it bears a (Ci~C6) alkyl group or a hydrogen atom. When J contains cyclcalkylene, J is preferably cyclc-hexylene. When J contains arylene, J is preferably phenylene cr naphthalene. When J represents - (CH2) a~L- (CH2) --, - (CH2) a-K-(CH2) b- or - (CK?) a"V0- (CH2) b-r s and b are preferably identical. The term "heteroarylene" means a divalent group corresponding to a heterocycle in which two hydrogen atoms have been replaced with two bonds. Heteroarylenes derived from the following heterocycles are preferred: fur an, thiopher.e, pyrrole, oxazcle, thiazole, imidazole, pyrazole, isoxazole, isorhiazcle, pyridine, pyridazine, pyrimidine, pyrazine, indolizine, indole, isoindole, benzofuran, benzothiophene, benzimidazole,, benzo thiazole, qui r.o line, isoquinolir e, cinnoline, phthalazine, quinazoline, naphthyridine and pteridine. The heteroarylene is very advantageously derived from imidazole, benzimidazole, pyrimidine or quinazoline. When J represents -M0-Q-M0-, Q is preferably (Ci-C2) alkylene or a bond, and M0 is preferably cyclohexylene or phenylene. The group J as defined above may bear one or more substituents chosen from a halogen atom, a Ci-C6 alkyl group, a Ci-Cg alkoxy group, an oxo group and a di(Ci-Ce) alkylamino group. Examples of diisocyanates that are particularly suit able are: - 1,2-diisocyanatopropane, - 1,4-diisocyanatobutane - 2,6-diisocyanatotoluene, - 1,12-diisocyanatododecane, - trans-1,4-cyclohexanediisocyanate, - 4,4'-diisocyanatodiphenylmethane, - 4,4' -diisocyanatx>-3, 3' -dimethyldiphenylmethane, - 1,5-diisocyanatonaphthalene. The condensation of the diisocyanate with the diphos-phine is performed under suitable conditions that are readily determined by a person skilled in the art. These polymerization conditions are preferably adjusted so as to obtain a polymer with a degree of polymerization of from 2 to 100, preferably from 5 to 100, for example from 2 to 50 and better still from 4 to 25. Polyureas with a degree of polymerization of from ..3 to 8 are particularly suitable for use. A person skilled in the art will select the degree cf polymerization such that the resulting polymer is insoluble in the solvent or mixture of solvents used in the asymmetric reaction that needs to be catalyzed. The choice of the polymerization method is not critical according to the invention. One particularly suitable method is solution polymerization. The solvent is generally a polar aprotic solvent chosen from an optionally halogenated aliphatic hydrocarbon, for example methylene chloride, chloroform, carbon tetrachloride cr 1,2-dichlorcethane; an optionally halogenated aromatic hydrocarbon, for example chlorc-benzene or dichlorobenzene; an ether such as diethyl ether, diisoproryl ether, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether and .glymes, and especially 1,2-dimechcxyethane; an amide such as formamide, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrciidir.cne cr hexamethylphcsphorylamide; a nitrile such as aceccnitrile cr isobutyronitrile; and dimethyl sulfoxide. The concentration cf reagents in the solution varies very widely as a function of the solubility of the reagents. It is generally between 0. 05 and 1 mol/1 ahd preferably between 0.01 and 1 mol/1, for example 0.1 mol/1. Preferably, the diisocyanate is used in slight excess relative to the diphosphine, although, strictly speaking, a stoichiometric ratio - of these two compounds may be suitable. Thus, the molar ratio cf the diisocyanate to the diphosphine is generally set at between 1 and 1.5, for example between 1 and 1.3. The temperature at which the polymerization is performed is determined as a function of the reactivity of the various reagents and of the desired degree of polymerization. As a guide, the temperature ranges between -20°C and 100°C, preferably between room temperature and 100°C, for example between 15 and 100°C and better still between 15 and 40°C. It is advantageously 20°C. The polymerization is performed conventionally by dissolving the reagents in the solvent, mixing, optionally heating the reaction medium, and then isolating the polymer, for example by filtration of the reaction medium. It will be noted that it may be necessary, before isolation of the polymer, to deactivate the ends of che polymer chain, and especially the unreacted iso-cya-nate functions, by addition of a Ci-Ce alkanol, for example propanol, isopropanol, methanol or ethanol, or even tert-butyl alcohol. An example of a polymer that is particularly preferred is a polymer containing as repeating unit: in which - Ri and Rn, which may be identical or different, represent a hydrogen atom cr a substituent, - Ari and Ar: independently represent an alkyl, ■alkenyl, cycloalkyl, aryl or arylalkyl group, - J has the meaning given above, - the degree cf polymerization is preferably between 2 and'100 and better still between 2 and 50. Pclyamides When the polymer is a polyamide, it may be prepared by condensation of a chiral diphcsphine bearing two amine-methyl functions with one or mere dicarboxylic acids cr activated derivatives thereof. The dicarboxylic acid advantageously corresponds to formula (Xb) below: HOOC-W-COOH Kb) in which W is as defined for J above. The preferred meanings of J indicated above are also preferred meanings of W. The group W may be substituted wizh one or more haicgen atoms or oxo, (Ci-Cs) alkyl,- (C:-Cf; aikoxy or di (C:-C5) -alkylamino groups. Among these dicarboxylic acids, the following are preferred: - the alipharic acids chosen from: - malonio acid, - succinic acid, - glutaric acid, - adipic acid, - 2,4-dimethyladipic acid, - pimelic acid, - suberic acid, - azelaic acid, - sebacic acid, - dodecanedioic acid, - fumaric acid, - maleic acid, - methyliminodiacetic acid, - 3-dimethylaminohexanedioic acid, - cycloalkanedicarboxylic acids and especially: - 1,4-cyclohexanedicarboxylic acid, - the aromatic dicarboxylic acids chosen.from: - phthalic acid, - isophthalic acid, - terephthalic acid, - phenylenediacetic acid, - 1,5-napnthalenedicarboxylic acid, - 4,4'-diphenyldicarboxylic acid, - 3,3'-diphenyldicarboxylic acid, - 4,4'-dicarbcxydiphenyl sulfone, - 3,3'-dicarboxydiphenyl sulfone. One particularly preferred group of dicarboxylic acids consists of the following acids: - succinic acid, - adipic acid/ - fumaric acid, - isophthalic acid, - terephrhalic acid, - 1,5-naphthalenedicarboxylic acid, - 4,4'-diphenyldicarboxylic acid, - 3,3'-diphenyldicarboxylic acid. The activated derivative of the dicarboxylic acid more generally denotes the dicarboxylic acid compound in which one or :wo of the carboxylic functions have been modified so as to increase their reactivity. Activated derivatives of dicarboxylic acid are obtained, for example, by formation of an anhydride bond cr of a group -COY in which Y is a halogen atom such as bromine cr chlorine. Other activated derivatives of dicarboxylic acids are chose bearing, instead of the carboxylic functions, groups -COT in which T denotes an azide, imidazoiide, p-nitrophenoxy, 1-benzotriazoie, N-O-succinimide, acyl-oxy (such as pivalcyloxy), (Ci-C: alkoxy)carbonyloxy, cr dialkyl- or dicycloalkyl-O-ureide group. The condensation of the diphosphine with the dicarboxylic acid or the activated derivative thereof is generally performed in a solvent. When the dicarbcxylic acid is used in unmodified form, it may be advantageous to perform the condensation in the presence of a catalyst, for example a strong acid such as hydrochloric acid or sulfuric acid, or alternatively in the presence of a coupling agent such as those commonly used in peptide synthesis. Among the known coupling agents that may be mentioned are N-hydroxylated derivatives such as N-hydroxy-succinimide and 1-hydroxybenzotriazoie; disulfides such as dipyridyl 2,2'-disulfide; succinic acid derivatives such as N,N' -disuccinimidyl carbonate;. phosphinic chlorides such as N,N'-bis(2-oxo-3-oxazolidinyl)phosphinic chloride; oxalates such as N,N'-disuccinimidyl oxalate (DSO), diphthalimide N,N'-oxalate (DPO), N,N'- * bis (norbornenylsuccinimidyl) oxalate (BNO), 1,1'-cis-(benzotriazolylL oxalate (BBTO), 1,1'-bis(6-chltro-benzotriazolyl) oxalate (BCTO) or 1, 1'-bis(6-trifluoro-methylbenzotriazolyl) oxalate (BTBO); triarylphosphines such as triphenylphosphine; a combination of a di (lower alkyl) azodicarboxylate and of a triarylphosphine, such as a combination of diethyl azodicarboxylate and of triphenylphosphine; N-(lower alkyl)-5-aryl-isoxazolium-3'-sulfonates such as N-ethyl-5-phenylisoxazolium-3' -sulfonate; carbodiimide derivatives, including N', N'-dicycloalkylcarbodiimides such as N' , N' -dicyclo-hexylcarbodiimide (DCC) or l-ethyl-3- (3-dimethylamino-propyl)carbodiimide (EDAPC); diheteroaryl diselenides such as di-2-pyridyl diselenide; arylsulfonyltri-azolides such as p-nitrobenzenesulfonyltriazolide; 2-halo-l-(lower alkyl)pyridinium .halides such as 2-chloro-l-methylpyridinium iodide; diarylphosphcryl-azides such as diphenylphosphorylazide (DPPA); imidazole derivatives such as 1,1'-oxalyldiimidazole or N,N'-carbonyldiimidazole; benzotriazole derivatives such as 1-hydroxybenzotriazole (HOBT); and dicarcox- imide derivatives such as N~hydroxy-5-norbornene-2, 3-dicarboximide (H0N3). Among these, carbodiimide derivatives are preferred. The reaction may take place within a wide temperature range. According to the reactivity of the reagents used, the reaction temperature ranges between -20°C and 100°C. When the polymerization involves the reaction of an activated derivative of the dicarboxylic acid with a diphosphine, a relatively low temperature, preferably of between 0°C and 40°C, is sufficient. Conversely, when the dicarboxylic acid_ is used in unmodified form in the reaction, the temperature is preferably between 50 and 80°C. The concentration of reagents in the reaction medium is not a determining factor according to the invention. It may range between 0.05 and 1 mci/1. In general, the mciar ratio of "he dicarboxylic acid cr of the activated derivative thereof to the diphosphine ranges between 0.E and 1.5 and preferably between 0. r ano ..z. A typical procedure, illustrating the preparation of a polyamide starting with a carboxylic acid chloride, is as follows. 3.75 mmol of "he carboxylic acid chloride are added to a solution of 4.16 mmol of diphosphine in 5 ml of N,N-dimethyiacetamide. The reaction mixture is stirred overnight at room temperature (18 to 30°C) . The poly- amide is then precipitated frorr. 150 ml of distilled water. The polymer is filtered off on a sinter funnel, and washed with water and then with isopropanol. The ■ general conditions for performing the polymerization and for isolating the polymer will be readily determined by a person skilled in the art, given that the preferred poiyamides of the invention have a degree of polymerization of between" 2 and 100,-for example between 5 and 100, preferably between 2 and 50 and better still between 4 and 25. A person skilled in the art will select the degree of polymerization such that the resulting polymer is insoluble in the solvent or mixture of solvents used in the asymmetric reaction that needs to be catalyzed. An example of a preferred polymer is a polymer containing as repeating unit: in which - Ri and R2, which may be identical or different, represent a hydrogen atom or a substituent, - Ari and Ar2 independently represent an alkyl, alkenyl, cycloalkyl, aryl or arylalkyl group, - W has the meaning given for J, - the degree of polymerization is preferably between 2 and 100 and better still between 2 and 50. Polyimides When the polymer is a polyimide, it may be prepared by condensation of a diphosphine bearing two aminoethyl functions with one or more tetracarboxylic acids or tetracarboxylic acid dianhydrides. For the preparation of these polyimides, a person skilled in the art may take inspiration from D.C. Sherrington, Cherru Commun. , 1993, 2275-2286. Advantageously, the polyimides -are prepared in two steps. In a first step, a polyamide is formed. This step is performed, for example, at a temperature of between 15 and 50°C and preferably between 20 and 30°C, in a polar aprotic solvent (such as an amide such as formamide, dimethylacetamide" cr N-methyl-2-pyrrolidinone, preferably dimethyiacetamide). In a second step, the polyimide is formed. This second step may be performed by treatment with a mixture cf acetic anhydride and pyridine at a temperature cf between -1CCCC and 10°C and preferably between -7 8 CC and -50CC. According to another variant of the invention, the polymer may be a polyurethane. Polyurethanes — When the polymer is a polyurethane, it may be prepared by condensation of a chiral diphosphine bearing two hydroxyl or hydrcxymethyl groups with a monomer of the diisocyanate type. In this case, a catalysis with a cin salt is often necessary. Reference may be made especially to the article by M. Lemaire ez al. J. l-Iol. Cat. A. 2002, Vol. 182-183, 239-247. According to one of Lzs aspects, the invention thus relates to a process for preparing a polymer of the invention, comprising the polymerization of a chiral diphosphine of formula (I') with one or more polymer-izable monomers, preferably of fcrmula (X); said chiral phosphine consisting of a .chiral substance bearing two identical functional groups capable of reacting with said polymerizable monomers. The invention also relates to the racemic polymer corresponding to the optically active polymer of the invention. This polymer may be prepared simply by polymerization of the appropriate diphosphine with one or more polymerizable monomers, said diphosphine bearing two identical functional groups capable of reacting with said polymerizable monomers. Preferably, the diphosphines used in this reaction are racemic diphosphines corresponding to the preferred chiral diphosphines defined above.. Thus, according to one preferred embodiment of the invention, the racemic diphosphine consists of a racemic base skeleton of formula (I') bearing two identical functional groups. Similarly, the polymerizable monomers preferably used for this polymerization are those described above for the preparation of the optically active .polymers. The operating conditions for this polymerization will be readily determined by a person skilled in the art by analogy with those proposed for the polymerization reaction leading to the optically active polymer. The diphosphines obtained according to the processes of the invention and those that are insolubilized in the form of a polymer as described above may be used as iigands in the preparation of metal complexes for the asymmetric catalysis of the following reactions: hydro-genation, hydrosilylation, hydroboration of unsaturated compounds, epoxidation of allylie alcohols, vicinal hydroxylation, hydrovinylation, hydroformylation, cyclopropanation, olefin isomerization, propylene polymerization, addition of - organometallic compounds to aldehydes, allylic alkylation, reactions of aldol type, DieIs-Alder reactions and, in general, reactions for formation of C-C bonds (such as allylic substitutions or Grignard cross-couplings). According to one preferred embodiment of the invention, the complexes are used for the hydrogenation of C=C, C=C and C=N bends. One subject of the invention is thus novel complexes comprising the chiral diphosphine of the invention cr the optically active polymer as defined above and a transition metal. As examples of transition -metals capable of forming complexes, mention may be made especially of metals such as rhodium, ruthenium, rhenium, iridium, cobalt, nickel, platinum and palladium. Among the- abcvementicr.ed metals, rhodium, ruthenium and iridium are preferred. Thus, according tc another cf its aspects, the invention relates tc the use of diohosohine ootionallv in insoluble form for the preparation of a metal complex of a transition metal intended for asymmetric catalysis, and more especially cf a ruthenium, iridium or rhodium complex. Specific examples cf said complexes of the present"" * invention are given hereinbelow, without any limiting nature. In the following formulae, P represents a ligand according to the invention, i.e. diphosphine or diphosphine insclubilized in the form of a polymer. A preferred group of rhodium and iridium complexes is defined by the formula: in which: - P represents a ligand according to the invention; - Yi represents an anionic coordinating ligand; - Me represents iridium or rhodium; and - Lig represents a neutral ligand. Among these compounds, the ligands that are particularly preferred are those in which: - Lig represents an olefin containing from 2 to 12 carbon atoms; - Yi represents an anion PF~~, PCle-, BF4", 3C14~, SbF6", ShCl5", B?h4", C104", CN~, CF3S03~, halogen, preferably CI" or Br"' a 1,3-diketonate, alkyl-carboxylate cr~ haloalkylcarboxylate anion with a lower alkyl (preferably of Ci-Ce) group, a phenyl-carboxylate or phenoxide anion in which the benzene ring may be substituted with lower alkyl (preferably Ci~C6) groups and/or halogen atoms. In formula (F:) , Lig2 may represent two ligands Lig as defined above or a bidentate ligand such as a linear or cyclic, polyunsaturated bidentate ligand comprising at least two unsaturations. It is preferable according to the invention for Lig2 to represent 1,5-cyclooctadiene or norbornadiene, or for Lig to represent ethylene. The term "lower alkyl groups" generally means a linear or branched alkyl group containing from 1 to 4 carbon atoms. Other iridium complexes are those of formula: in which Lig, P and Yi are as defined for formula ' f- - A preferred group of ruthenium complexes consists of the compounds of formula: in which: - ? represents a ligand according to the invention; - -Yi1 and Y-J, which may be identical or different, represent an anion PF6~, PCI:", BF4", BC14", SbF^", SbCl6~, B?h4", CIO;"/ CF3SO3", a halcgen atom, mere particularly chlorine or bromine, or a carboxylase anion, preferably acetate or trifluoroacetate. Other ruthenium complexes are those corresponding 00 formula XIV below: in which: - P represents a ligand according 00 the invention; - ar represents" benzene, p-methyiisopropyibenzene :r hexamethylbenzene; - Yi3 represents a halogen atom, preferably chlorine or bromine; - Yi4 represents an anion, preferably a ??f, rCI-;", BF4~, BC1T, 3bF6~, SbCl5V. 3Phr, C104" or CF3SC3" anion. It is also possible to use in the process of the invention complexes based on palladium and platinum. As more specific examples of said complexes, mention may be made, inter alia, of Pd (hal) 2P and Pt (hal) -? in which P represents a ligand according to the invention and hal represents halogen, for instance chlorine. The complexes comprising a ligand according to the invention and the transition metal may be prepared according to the known processes described in the literature. The complexes are generally prepared from a pre-catalyst, the nature of which varies according to the transition metal selected. In the case of rhodium complexes, the precatalyst is, for example, one of the following compounds: [RhI(CO)2Cl]2; [Rh1 (COD) CI] 2 in which COD denotes cyclo-octadiene; or Rh1(acac)(CO)2 in which acac denotes acetylacetonate. In the case of ruthenium complexes, precatalysts that are particularly suitable are bis(2-methylallyl)cyclo-octa-1, 5-dieneruthenium and [RuCl2 (benzene) ] 2. Mention may also be made of Ru(COD) (ri3-(CH2) 2CHCH3) 2. By way of example, starting with bis(2-methylallyl)- cycloocta-1, 5-dieneruthenium, a solution or suspension containing the metal precatalyst, a ligand and a fully degassed solvent such-as acetone (the ligand concentration of the solution or suspension ranging between 0.001 and 1 mol/1) is prepared, to which is added a methanol ic solution of hydrobromic acid. The ratio of the ruthenium to bromine advantageously ranges between 1:1 and 1:4 and preferably between 1:2 and 1:3. The molar ratio of the ligand to the transition metal is about' 1. It may be between 0.8 and 1.2. When the precatalyst is [RuCl2 (benzene) ] 2, the complex is prepared by mixing together the precatalyst, the ligand and an organic solvent and optionally maintaining at a temperature of between 15 and 150°C for 1 minute to 24 hours and preferably from 30 to 120CC for 10 minutes to 5 hours. Solvents that may be mentioned include aromatic hydrocarbons (such as benzene, toluene and xylene), amides (such as formamide, dimethyifcrmamide, dimethylacet-amide, N-methyl-2-pyrrolidinone or hexamethylphos-■ phorylamide) and alcohols (such as ethanol, methanol, n-propanol and isopropanoi), and mixtures thereof. Preferably, when the solvent is an amide, especially dimethyl formamide, the mixture of the ligand, the precatalyst and the solvent: is heated to between 8 0 and 1203C. As a variant, when the solvent is a mixture of an aromatic hydrocarbon (such as benzene) with an alcohol (such as ethanol) , the reaction medium is heated to a temperature of between 30 and 70°C. The catalyst is then recovered according to the standard techniques (filtration or crystallization) and is used in asymmetric reactions. However, the reaction that needs to be .catalyzed by the complex thus prepared may be performed without intermediate isolation of the catalyst complex. The case of hydrogenation is outlined in detail in the text hereinbelow. The unsaturated substrate, dissolved in a solvent comprising the catalyst, is placed under hydrogen pressure. The hydrogenation is performed, for example, at a pressure ranging between 1.5 and 100 bar and at a temperature of between 20°C and 100°C. The exact operating conditions depend on the nature of the substrate that needs -to be hydrogenated. However, in the general case, a pressure of from 20 to 80 bar and preferably from 40 to 60 bar, and a temperature of from 30 to 70°C are particularly suitable. The reaction medium may. consist of the reaction medium in which the catalyst was obtained. The hydrogenation reaction is then performed in situ. - - As a variant, the catalyst is isolated from the reaction medium in which it was obtained. In this case, the reaction medium of the hydrogenation reaction consists of one or more solvents, chosen especially from C1-C5 aliphatic alcohols, such as methanol or propanol, and an amide as defined above, preferably dimethylformamide, optionally as a mixture with benzene. When the hydrogenation reaction is performed in situ, it is desirable to add to the reaction medium one or more solvents chosen from these mentioned above and more particularly one or more aliphatic alcohols. According to one preferred embodiment, fully degassed methanol and the substrate are added to the reaction medium containing the complex. The amount of methanol, cr more generally of solvent, that may be added is such "hat the concentration of the substrate in the hydro-genation reaction medium is between 1 x 10 and 10 mol/1 and preferably between 0.01 and 1 mcl/1. The molar ratio of the substrate to the catalyst generally ranges from 1/100 to 1/lOC 000 and preferably from 1/20 to 1/2000. This ratio is, for example, 1/1000, Zhe removal of the catalyst from the reaction medium is facilitated when the ligand used is in the form of a polymer. The catalyst is separated from the reaction medium ry nanof i It rat ion or ultrafiltration.. The technique of nanof iltraticn is more particularly suitable in the case of catalyses of polymer type. The application of this technique is illustrated, for example, in Tetrahedron: Asymmetry, Vol. 8, No 12, 1975-1977, 1997. One advantage of the process of the invention is chat the recovered catalyst may be readily recycled without loss of activity. The ruthenium, rhodium and iridium complexes prepared using the iigands of the invention are more especially suitable for the asymmetric catalysis of asymmetric hydrogenation reactions. The ruthenium complexes prepared using the Iigands of the invention are more especially suitable for zhe asymmetric catalysis of hydrogenation reactions of C=0 bonds, C=N bonds and C-C bends and preferably C=C bends of a,p-ethylenic carboxylic acids. As regards the hydrogenation of double bonds, the suitable substrates are of a, p-unsaturated carboxylic acid type and/or derivatives of a, p-unsaturated carboxylic acids. These substrates are described in EP 95943260.0. The a,p-unsaturated carboxylic acid and/or rhe derivative thereof more particularly corresponds to formula A: in which? - Ri, R2, R3 and R4 represent a hydrogen atom or any hydrocarbon-based group, insofar as: . if Ri is different than R2 and different than a hydrogen atom, then R3 may be any hydrocarbon-based group or functional group denoted by R, . if Ri or R2 represents a hydrogen atom and if Ri is different than R2, then R3 is different than a hydrogen atom and different than -COOR4, . if Ri is identical to R2 and represents any hydrocarbon-based group or functional group denoted by R, then R3 is different than -CH-(.R)2 and different than -COOR4 - one of the --groups Rlf R2 and R3 possibly representing a functional croup. k specific example that may be mentioned, inter alia, is 2~methvl-2-butenoic acid. A first group of preferred substrates is formed by the substituted acrylic acids that are precursors of amino acids and/cr derivatives. The term "substituted acrylic acids'7 means the set cf compounds whose formula is derived from that of acrylic acid by substitution of at least two of the hydrogen atoms borne, by the ethylenic carbon atoms with a hydrocarbon-based group or with a functional group. They may be symbolized by the following chemical formula: in which: - R5 and R'~., which may be identical or different, represent a hydrogen atom, a linear or branched alkyl group containing from 1-to 12 carbon atoms, a phenyl group or an acyi group containing frem 2 to 12 carbon atoms, preferably an acetyl or benzoyl group, - R8 represents a hydrogen atom, an alkyl group containing" from 1 to 12 carbon atoms, a cycloalkyl group containing from 3 to 8 carbon , atoms, an arylalkyi group containing from 6 to 12 carbon -atoms, an aryl^ group containing from 6 to 12 carbon acorns or a heterocyclic group containing from 4 to 7 carbon atoms, - Rio represents a hydrogen atom or a linear or branched alkyl group containing from 1 to 4 carbon atoms. Mention may be made more particularly of: - methyl a-acetamidocinnamate, - methyl acetamidoacrylate, - benzamidecinnamic acid, - a-acetamidocinnamic acid. A second preferred group of substrates consists of itaconic acid and derivatives thereof of formula: v . in which: - R1: and R12/ which may be identical or different, represent a hydrogen atom, a linear or branched alkyl group containing from 1 to 12 carbon atoms, a cycloalkyl group containing from 3 to 8 carbon atoms, an arylalkyl group containing from 6 to 12 carbon atoms, an aryl group containing from 6 to 12 carbon atoms or a heterocyclic group containing from 4 to 7 carbon atoms, - R1C and R';o, which may be identical or different, represent a hydrogen atom or a linear or branched alkyl group containing from 1 to 4 carbon atoms. More particular examples that may especially be mentioned include itaconic acid and dimethyl itaconate. k third preferred group of substrates is defined by formula (A3) : in which: - R":o represents a hydrogen atom or a linear or branched alkyl group■ containing from 1 to 4 carbon atoms, - Ri3 represents a phenyl or naphthyl group option ally bearing one cr more substituents. Specific examples that may be mentioned include the substrates leading via hydrogenstion to 2- (3-benzoyl-phenyl) propionic acid (Ketoprofen®) , 2-(4-isobutyl-phenyl)propionic acid (Ibuprofen®} and 2-(5-methcxy-naphthyl)propionic acid (Naproxen®). As regards the hydrcgenation of carbonyl bonds, the ruthenium complexes are more particularly suitable for the asymmetric catalysis of hydrogenation reactions of the C=0 bonds of (3-keto esters, of a-keto esters cr of ketones. The appropriate substrates of ketone type more preferably correspond to formula (B): in which: - R14 is different than R15, - R14 and R15 represent a hydrocarbon-based group containing from 1 to 30 carbon atoms optionally comprising one or more functional groups, - Rx4 and Ri5 may form a ring optionally comprising another hetero atom. These compounds are described specifically in FR 96/08060 and E? 97S30607.3. One preferred group of ketone compounds corresponds to formula (B) in which R14 and R15 represent, independently of each other: - an alkyl chain, preferably of Ci to Ci0, optionally interrupted with one or more oxygen or sulfur atom(s) or carbonyl function(s) and optionally substituted with one or more halogen atoms or carboxyl groups, - an alkenyl or alkynyl chain, preferably of C2 to Cio/ optionally interrupted with one or more oxygen or sulfur atom(s) or carbonyl function(s) and optionally substituted with one or more halogen atom(s) or carboxyl group(s); - an aryl group, preferably of C€ to C12, optionally substituted with one or more halogen atom(s) or alkyl or alkenyl group (s); -- an arylalkyl group, preferably of C7 to d=, optionally substituted with one or more halogen atoms; - an arylalkenyl group, preferably of C8 to C:=, optionally substituted with one or more halogen atoms; and - * indicates the optional presence in R15 of an asymmetric center located in the position a to the carbonyl function. By way of representation of the substituents R:5 containing an asymmetric center, mention may be mace particularly of groups Ri5 in which the carbon at cm bearing the asymmetric center is substituted with a mono- or disubstituted amine function and with an ester function. According to one particularly preferred embodiment of the invention, the substrate is a. p-keto ester (such as ethyl acetoacetate cr methyl 3-oxovalerate), an a-keto ester (such as rr.ethyl benzoylformace or methyl pyruvate), a ketone (such as acetopher.one) or an 3,(5-ethylenic carcoxylie acid (such as icaconic acid) cr an unsaturated amino acid cr a derivative "hereof (such as , methyl 2-acetamidcacryla~e;. The invention moreover relates co the use of a combination of a chiral diphosphine or of an optically active polymer according :o the invention wi~h a chiral or achiral diamine, for the selective reduction of ketones. Advantageously, a chiral diamine is used in "his combination. The diamines chat may be used for this purpose -are "he optically active diamines described in WO 97/20789 and the corresponding racemic diamines. According to one particularly preferred embodiment of the invention, the diamine is 1,2-diamino-l, 2-dipher.yl-ethane; 1,1-bis(p-methoxyphenyl)-2-methyl-l,2-diamino-ethane; 1,1-bis(p-methoxyphenyl)-2-isobutyl-l, 2-di-aminoethane; or 1,1-bis(p-methoxyphenyl)-2-isopropyl-1,2-diaminoethane. Examples of chiral diamines are more particularly those of formula: in which G4 is alkyl, for example methyl, isobutyl or isopropyl. Mention will be made more particularly of the achiral ethylenediamine and of achiral or chiral 1,2-diamino-1,2-diphenylethane, such as R,R-l,2-diamino-l, 2-diphenylethane . The ketones that may be reduced according to this process are those described above. The conditions for performing the reduction are those generally described above. The invention also relates to the use of the combination of an achiral diphosphine or cf a racemic polymer, according to the invention, with a chiral diamine, for the selective reduction of ketones. The chiral diamine that may be used is as described in WO 97/2C'789, the ketones and the operating conditions being as defined above. The rhodium complexes prepared from the ligands of the invention are mere especially suitable for the asymmetric catalysis of olefin isomerization reactions. The use of a ligand of formula ' Ia3) or polymers derived therefrom such as polyurea, pclyamide cr polyimme intended for the asymmetric catalysis of hydrogenation reactions, forms a preferred subject of the invention. The examples ihat follow more specifically illustrate the invention. The meaning of the abbreviations used is given below. The examples that follow illustrate the invention more specifically. Example 1: Preparation of 5,5'-dibromoBINAPO: Preparation of BINAPO: (S)- or (R) -3INAP (2,2'-bis (diphenylphosphi.no)-1,1'-binaphthyl) (3 g, 4.81 mmol, 1 eq.) dissolved in 100 mL of CK?Cl2 is placed in a 250 mL round-bottomed flask. The mixture is cooled to 0°C and 10 mL of 35% by weight aqueous hydrogen peroxide solution are added. The mixture is stirred while being allowed to return :o room temperature, for four hours. 100 ml of water are then added. The organic phase is separated out and the aqueous phase is extracted with CH2CI:. The combined organic phases are washed with saturated sodium bisulfite. The solution is checked for the absence of peroxide, and is then dried over sodium sulfate and evaporated. A white solid is obtained (m = 3.14 g, 4.8 mmol, i.e. quantitative yield). The characterization of the diphosphine in dioxide for™ (BINAPO) is as follows: - XE NMR (300 MHz, CDC13): 6.80 (d, 4K, J = 3.7), 7.2- 7.3 (m, 8H), 7.3-".5 (m, 12H) , 7.6-7.7 ;m, 4H) , 7.8-7.9 (m, 4H) " 31P NMR (81 MHz, CDC13) : 28.67 melting point: 256-258°C Preparation of 5,5-dibromoBINAPO: Iron filings (622 rug, 11.1 mmol, 1.5 eq.), 65 mL of CCr4 and dibromine (7.6 mL, 148 mmol, 20 eq.) are placed in a dry 100 mL... round-bottomed flask equipped with a condenser and a CaCl2 guard tube. The mixture is heated to 70°C, followed by portionwise addition of BINAPO (4.8 g, 7.4 mmol, 1 eq. ) dissolved in 45 mL of CC14. The mixture is stirred at 70°C for 3 hours. After checking by thin layer chromatography that the reaction is complete, the mixture is transferred into a separating funnel and washed with water, with sodium bisulfite, with sodium bicarbonate and then with brine. The resulting solution is dried over sodium sulfate and then filtered through silica and eluted with ethyl acetate. The solution thus obtained is evaporated under reduced pressure (about 8 mmHg). A white solid is obtained jm- = 4.83 g, 6 mmol, i.e. a yield of 80.7%) . The characterization of the diphosphine (PO) in dibromo form is as follows: - *H NMR (200 MHz, CDC13) : 6.62 (t, 2H, J = 15.0), 6.72 (d, 2H, J = 9.0), 7.2-7.5 (m, 22H) , 7.55 (dd, 2H, J = 3.0; 21.0), 7.6-7.8 (m, 4H), 8.3 (dd, 2K, J = 1.7; 9.0) - 31P NMR (81 MHz, CDC13) : 29.20 - melting point > 300°C Example 2: — Preparation of 5,5'-dicyanoBlNAPO: 5,5' -DibromoBINAPO (4.7 g, 5.8 mmol, 1 eq.) and copper cyanide '1.04 g, 16.24 mmol, 2.8 eq. ) are placed in a 250 mL round-bottomed flask under an inert atmosphere, equipped with a condenser. The mixture is dissolved in 7 0 mL of DMF and is ref iuxed overnight;. The mixture is cooled and then treated with a solution of ethylenediamine (25 mL) and water (25 mL). The mixture is stirred for 2 minutes, and 100- mL of v;ater and 200 mL of toluene are then added. The mixture is stirred for 5 minutes and the aqueous phase is then extracted once with toluene. The' combined organic phases are successively washed once with water, four times with HC1, once with brine and then once with sodium bicarbonate. The product is then dried over sodium sulfate, and then evaporated under reduced pressure (about 8 nutiHg) (m = 3.71 g, 5.5 mmol, i.e. a yield cf 90.8%). The product is purified cr. a column of silica gel, eluting with ethyl acetate/cyclchexane (4/6). 2.52 g (3.75 mmol, i.e. a yield cf 61.7%) of pure white product are obtained. The characterization of the diphosphine (PO) in dicyano form is as follows: - *H NMR (200 MHz, CDC13) : 6.85 ;dd, 2H, J = 7.0; 7.1), 6.97 (d, 2H, J = 9.0) , 7.2-7.5 (m, 24H) , 7.6-7.7 {-f 6H) , 7.8 (dd, 2Hf* J = 1.1; 6.1), 8.33 (dd, 2H, J = 1.9; 7.1) - 31P NMR (81 MHz, CDC13) : 2 9.1 - ESI+ mass: MH" = 705 - melting point > 300°C Example 3: Preparation of 5,5'-dicyanoBINAP: 5,5' -DicyanoBIMAPO (420 mg, 0.6 mmol) is placed in a dry 25 mL round-bottomed flask under an inert atmosphere, equipped with a condenser. Phenylsilane (8 mL, 64.8 mmol) is added and the suspension is degassed under reduced pressure (about 8 mmHg) and argon is introduced. The mixture is heated to 130°C and trichlorosilane is added in three portions (3 * 1 mL) after 1 hour, 3 hours and then 15 hours; the mixture is then s-irred for a further 2 hours. The resulting mixture is cooled and the product is evaporated to give a white solid. This solid is washed with cyclohexane, filtered on a Millipore filter and then dried under reduced pressure (about 8 mmHg). Pure (S) or (R) products are obtained in quantitative yields. The characterization of the diphosphine in dicyano form is as follows: - XE NMR (300 MHz, CDC15) : 6.63-6.81 (m, 4H) , 7.04-7.30 (m, 20H) , 7.42 (d, 2H, J = 7.14) , 7.56 (d, 2H, J = 8.%85) , 8.33 (d, 2H,. J = 9.03) - - 31P NMR (81 MHz, CDC13) : -13.99. Example 4: Preparation of 5, 5' -diaminomethylBIKAP: 5,5'-DicyanoBINAP (400 mg, C.6 mmcl) is placed in a 100 mL round-bottomed flask under an argon atmosphere. The product is dissolved in a »'I:1) mixture of 22.5 mL of THF and 22.5 mL of toluene. L1AIK4 (227.7 mo, 6 mmol) is then added portionwise. The mixture is heated at 105GC for 2 hours. The resulting mixture is cooled, and 0.5 mL of water and 0.5 mL of sodium hydroxide solution (15% by mass; are then added. After stirring for three minutes, 1.5 g of Celite are added. After five minutes, the mixture is then filtered and the residue is washed with dirhloromethar.e. The filtrate is evaporated and then dried under reduced pressure (about 8 rrinHg) to give a yellow-white solid. The product is obtained in quantitative yield. The characterization of the diphosphine in diaminomethyl forn is as follows: - XH NMR (200 MHz, CDC13) : 1-62 (3, 4H) , 4.37 (s, 4H) , 6.8-7.0 (m, 4H) , 7.1-7.3 (m, 2OH) , 7.3 6 (df 2H, J = 6.58), 7.51 (d, 2K, J = 8.82), 3.15 (d, 2H, J = 8.82) - 31P NMR (81 MHz, CDCI3) : --15.50 - 13C NMR (50 MHz, CDC13) : 4 4.30;- 122. 92; 125.61; 125.93; 127.32; 128.12; 128.30; 128.44; 128.71; 129.02; 12 9.31; 130.04; 132.57; 132.83; 133.18; 133.81; 135.23; 139.42 - aD (c = 1, DMF): -100.3 for (S) - aD (c = 1, DMF): +101.4 for (i?) Example 5 1 - Hydrogenation test: The procedure followed is given below. 5,5'-DiamBINAP (17.5 mg, 0.0235 mmol, 1 eq.) dissolved in 1 mL of dichloromethane is placed in a 5 mL vial under an inert atmosphere, bis(2-methylallyl) cycloocta-1, 5-dieneruthenium (II.) complex (7.5 mg, 0.0235 mmol, 1 eq.) is added and the mixture is stirred for 30 minutes. The solvent is then evaporated off. 1 ml of methanol (or ethanol) is added and the substrate is then placed in an ^autoclave under a' " hydrogen pressure of 40 bar at 50°C and stirred for 15 hours. The autoclave is then cooled and depressurized. The solution is filtered through Celite and then analyzed by gas chromatography. 2 - Hydrogenation of ethyl or methyl acetoacetate This is performed as described above with a substrate/catalyst ratio of 1000. The results obtained are as follows: These results are confirmed v:hether 5, 5' -diamBINAP is used in (S) or {R) form. The configuration of the corresponding alcohol obtained depends on the chiraiity of the ligand used. Examoies 6 and 7 ■*- Preparation of ,R) -5, 5f-perflucrohexylBINAPQ and (R' -5,5f-perfluorooccylBINAPO - 5, 5'-DibromoBINAPO (2.46 mmoi, 1 eq.), copper powder (14.76. mmol, 6 eq.) and the alkyl iodoperfluoride 25 m * 0.25 mm column. The results obtained are giver, ir. the following rable: The hydrogena~ion of ethyl acetcacetate leads to ethyl 3-hydroxybutyrate. Example 14 Hydrogenation of 2-methylacetamidoacrylate using the catalyst prepared in example 13 Degassed anhydrous ethanol is added to the reactor in which the catalyst has just been prepared. The substrare is then added (in a defined catalyst/substrate ratio). The reactor is placed in an autoclave under a hydrogen pressure of 4C bar and at 50°C. Stirring is maintained for 6 hours. The reactor is recovered and then centrifuged. The supernatant solution is recovered and then analyzed by gas chromatography. The determination of the enantiomeric excess is performed by chiral gas chromatography on a i3dex A 60 m CLAIMS I. A diphosphine in racemic form or in chiral form, corresponding to formula (I): in said formula: - Ri and R?, which may be identical or different, represent a hydrogen atom or a substituer.t, - Ari and Ar2 independently represent an alkyl, alkenyl, cycloalkyl, aryl or arylalkyl group, - Xi and X2, which may be identical or different, represent: . a group R, alkyl, alkenyl, alkynyl, cycloalkyl, aryl or arylalkyl, . an alkyl group substituted with one or more halogen atoms, preferably fluorine, or with nitro or amino groups, . a halogen atom chosen from bromine, chlorine and iodine, . an -OK group, . a group -0-CORa, . a group -0-Ra, . a group -S-Ra, a -CN group, . a group derived from the nitrile group such as: . a -CH2-NH2 group, a -COOH group, . a group derived from the carboxylic group such as: a group -COORa, . a -CH2OH group, . a group -CO-NH-Rb, . a group derived from the aminomethyl group such as: . a group -CH2-NH-CO-Rb, . a group -CH2-NH-CO-NH-Rb, . . a group -CH2-N=CH-Ra, . a -CH2-N=O0 group, a -CH2-NH4+ group, a group comprising a nitrogen atom such as: . a group -NHRa, . a group -N(Ra)2, a group -N=CH-Ra, an -NH-NH2 group, an -N=N+=N~ group, an -N=C=0 group, a magnesium or lithium atom, in the various formulae, Ra represents an alkyl, cyclcalkyl, arylalkyl or phenyl group and Rb has the meaning given for Ra and also represents a naphthyl group. 2. The ciphosphine as claimed in claim 1, bearing two functional groups capable of reacting with one or mere polymerizable monomers corresponding 'to the general formula (1'): in said formula: - Ri and R2/ which may be identical or different, represent a hydrogen atom or a substituent, - Ari and Ar? independently represent an alkyl, alkenyl, cycloalkyl, aryl or arylalkyl group, - Xi and X2, which are identical, represent: an -OH group, . a -CH2OH group, " . a -CH2-NH2, . a -COOH group, . a group -COORa in which Ra represents an alkyl, cycloalkyl, arylalkyl or phenyl group, . an -N=C=0 group, - a -CH2-N=C=0 group. 3. The diphosphine as claimed in either of claims 1 and 2, characterized in that it corresponds to formula (I) or (I') in which Arx and Ar2 represent a (Ci-C6)alkyl group, a phenyl group optionally substituted with one or more (Ci-C6) alkyl or (Ci-Ce) alkoxy; or a (C4-C8)cycloalkyl group optionally substituted with one or more (Ci-C5)-alkyl groups. 4. The diphosphine as claimed in one of claims 1 to 3, characterized in that it corresponds to formula (I) or {I') in which Ri and R2, which may be identical or different, represent a hvdroger. atom or an alkyl or alkoxy group containing from 1 to 4 carbon atoms. 5. The diphosphine as claimed in one of claims 1 to 4, characterized in that it corresponds to formula (I) or (I' ) in which Ari and Ar2 represent a phenyl group and R: and R2 represent a hydrogen atom. 6. The diphosphine as claimed in one of claims ■ 1 to 5, characterized in that it corresponds to formula (I) or (I' ) in which Xi and X2, which are identical, represent: . a halogen atom, preferably a bromine or chlorine atom, . an alkyl group substituted with one or more fluorine atoms, . a -CN group, " . a -CH2-NH2 group, . a- -COOH group. 7. A diphosphine in dioxide form, in racemic form or in chiral form corresponding to formula (II): in which Xi, X:, R:, R2, Ar: and Ar2 have the meaning given for formula (I) in one of claims 1 to 5. £ . The diphosphine or diphosphine in dioxide form as claimed in one of claims 1 to ~, characterized in that it corresponds to one of the following formulae: in which p is between 1 and 15 and preferably between 6 and 10, q is between 3 and 21 and preferably between 13 and 25, and Ri, R2, Ari and Ar2 have the meaning given for formula (I) in one of claims 1 to 5. 10. A process for preparing a diphosphine or a diphosphine in dioxide form corresponding to formula ;i), (.J/) or (II) ' described in one, of claims 1 to 9, characterized in that it comprises at least one step of halogenation in position 5,5' of a compound of formula (III) : . in said formula: R:, R:, Ari and Ar2 have the meaning given above in one cf claims 1 ro 5. 11. The process as claimed in claim 10, characterized in that the halogenation is performed in an inert aprotic solvent, preferably 1,2-dichioroethane. 12. The process as claimed in claim 10, characterized in that the diphosphine in dioxide form of formula 'I' "OQ^^'^^Ci ^ — — .-> v- *— 11 "j p. [ ~ '.' \ • in said formula: cr.e cf claims 1 tc 5. j : . t\ 010-^53 J_-^_ O -L_ T^ ^ d .'-._■ i_ i ± ~: -*. _ ^ . . ^ c ■ -tz; r.^.-•-rpcnr'- ^ -i p™ — •-•) — ^ v-w - ' ~! ^ ' r ' ~ -- """ ' "i ^ ^ cr ■"■ -— - -^ CL. Uw_ LC J^^..^li-v _vj — ■ r*-. ■" '-' 1 a "i 7T", c; 1 ~ ~ £ ~ n "'/""" "* ^/i_ l_* _1_ CI J_ 11. 3 J_ —^ _i ^ __ i i. •■J..^_wii ^A-_ —* * *- - - _ J_ 'w fc»/ -i_ w w ^. . _ — ■—*. -_wv., . ^ -^ -^ .. . a:cm, characterized in that in cemprises the following seeps: i) performing one halogenation on ohe 5,5' cosloo on of a compound of formula (III): in said formula: - - - Ri, R2/ ~.r: and Ar: have ohe meaning giver, above in one cf claims 1 to 5, using a halogen and in the presence of iron, so as to obtain ohe co rresponding dihaio compound o.f formula: in said formula: - X represents a chlorine, bromine or iodine atom, - Ri/ R?/ Ari and Ar: have the meaning given above in one of claims 1 to 5; ii) performing the reduction of 'he diphosphine in dioxide and dihalo form in position 5,5' of formula ;ila:), into the diphosphine of formula (Iai) : in said formula :■ - X represents a chlorine, bromine or iodine atom, " Rif Rif Ar: and Ar: have z'r.e meaning given above in one of claims 1 to 5. 14 . A process for preparing the diphosphine corresponding to formula {1) cr (I7 ) described in one in said formula: - X represents a chicrine, bromine or iodine ao:m, - ?.:, R2f ----i and Ar: nave the meaning given above on one of claims 1 to 5, using a suitable nucleopnilic reagent so as no oooain one corresponding dicyano compound (Ila?): in said formula: - ?-:/ R2f -1--! ^-d Ar2 have the meaning given above in .one of claims 1 to 5, ii) performing the reduction of The diphosphine in dioxide and dicyano form in position 5,5' of formula (Ilaa) into the diphosphine of formula (Ia2) : in said formula: • Ri/ R2/ -^r- anc^ Ar2 have the meaning given above in one of claims 1 to 5. 15. The process as claimed in claim 14", characterized in that the cyanation is performed using copper cyanide. 16. The process as claimed in either of claims 13 and 14, characterized in that - the reduction of the diphosphine in dioxide form is performed using a hydrcgenosilane of formula: HSiR,.RpRc ;ra: in said formula: - Ra, Rp and R6, which may be identical or different, represent a hydrogen atom, an alkyl group containing frem 1 to 6 careen atoms, a phenyl group or a chlorine atom, - at mo.st two of the groups R., Rp and R5 represent a '", ' / ir* s-1 ,-«, v~ -s- ^ ^~^'~iZ2.-'~J - v~ "^v*"^. ' ■ N^ _ J O ■■—' W 1 X 1 . 'M ,- W --»--■■ ^ --A %-- _l ^, ^ 'J ^ J. J>_/ s_, _A _-* _• _» ^ v- ,"■. ]" "*^ ,^" a *^"2 i^*-^■^' ?op -" — -" — —* - — -,^-n~v~,^~=::=:i~^ -% ._, _ ^ ,^ ^~ {' ~ a ~"' cescric^d i *~ c _ a t T 14 1 e a ct n O to t r e ^-, ,-* v~ v ;" y^ /~ -v -^ — *"> " 7 --" ^ -vi -i^. -. - - »~ ^ ^-, — — /-, -.•--■"^ • i ^ .' '^ - • -_'vJj_-_v--5'wO->-*._Lii'-H .i^GiUj-ii'v — _-_*-/ — , v.v'i'.'.vw -» — -^i. _-_ — ~~s — ..:w — ._* , — '—*■ _*. • in said formula: - Rir ?-2f t\~i and ?.~z have the meaning given above in one of claims 1 to 5. 19. The process as claimed in claim 18, characterized in that the reduction is performed using lithium aluminum hydride (LiAlHa) . 20. A process for preparing the dichisphine corresponding to formula (I) or !!'/ described in one of claims 1 to 5 in which Xi and X: represent a -10CH group, characterized in that ' it ' comprises the steps defined in claim 14 and then a step consisting in treating, in acidic medium . cr in basic medium, the compound of formula (Ia2) , so as to obtain the corresponding carboxylic acid of formula (Ia4) : in said formula: - R:f H-, Ari- and Ar2 have- the meaning given above in one cf claims 1 to 5. 21. A process for preparing the diphosphine corresponding to formula (I) cr (I') described in one of- claims 1 to 6 in which Xi and X2 represent a group -C00?.a in which Ra represents an alkyl, cycloalkyl, aryialkyl* or phenyl group, characterized in that the direct esterification of the compound of formula (la^) described in claim 20 is performed, in basic medium. 22. A process for preparing the diphosphine corresponding to formula (1) cr (I' ) described in one cf claims 1 to 6 in which Xi and X2 represent a -CH2OH group, characterized in that reduction of the compound of formula (Ia4} described in claim 20 is performed, preferably using LiAlH4 or NaH. 23. A process for preparing the diphosphine corresponding to formula (1) cr (I' ) described in one of claims 1 to 6 in which Xi and X2. represent a group .-^ ^ v- v" *^ ^ y> s-\i *-» —, -i v-v ^* — ^ — -^ v* ^^ - - ^ * .^ ^ ' ~T ^ n ^ "^ "■** "■ -**^ .n """ -— ^_ — (J H ^ — Nj J-t — :J ^ c .^ J"_ "- W " 1 Z " - ^^Qv-^-0-"-; ^. — ^ __•""' _ "p /*> y T) I'l^l 2--.^ "i £S " ■"* '• ' ^ £7^ -"-• --" ~" : :Z ^ "" i *rf ~ -C^ ,*> ^ *•** — ^-. v* yo ^.—^ ". 7 ~ — " :Z. ^ acid Rb-C10H in ::.e present zf ~ coupling agent. of claims 1 :o c in which X-_ and X? represent a :r:u; -CH2-NH-CC-NK-Rb, in which Rc represents an alkyl, cycloalkyl, arylaikyl, phenyl or naphchyl grzup, characterized in that the reaction cf the compound zf formula (Ia3; described in claim 18 is performed, wzzh an isocyanate Rb-^CO, generally in solvent medium. 2 6. A process for preparing the diphoschz.ne corresponding to formula (I) or (I') described in one of claims 1 to 5 in which Xi and X2 represent a grzup —CH2-N=CK-Ra/ in which Ra represents an altyl, cycloalkyi, arylaikyl or phenyl group, characterized in that the reaction of the compound of formula la3 described_ir. claim IS is performed, with an aldehyce Ra-CHO. 27. A process for preparing the diphzzzhzne C /-»i v- ■>" id o T" i""1 """' ^ ~ -r~ ■*• -*- .—_ of claims -1 to 6 in which X: and X: represent a zrzuz -CH2-N=C=0, characterized in that the reaction of the compound of formula (las) with phosgene is performed. 28. A process for preparing the diphosphine corresponding to formula (I) or (I' ) described in one of claims 1 to 6 in which Xi and X2 represent a -CH2-NH4+ group, characterized in that the reaction is performed by placing the compound of formula (Ia3) in contact with an acid, preferably hydrobromic acid, at room temperature, in a suitable solvent capable of dissolving the compound of formula (183) . 29. A process for preparing the diphosphine corresponding to formula (I) cr (I') described in one of claims 1 to. 6 in which X: and X2 represent, respectively, a group -NHRa or a group -N(Ra)2 in which Ra represents an alkyi, cycloalkyl, arylalkyl or phenyl group, characterized - in that the reaction, respectively, of the diphosphine in dioxide and dihalo form of formula (Ilai) described in claim 13 and of an amine RaNH2 or (Ra) 2NH is performed, followed by a reduction of the diphosphine in dioxide form as described previously in either cf claims 16 and 17. 30.. A process for preparing the diphosphine corresponding re formula (I) cr ;i') described in one of claims 1 to 5 in which. Xi and X2 represent a group -N=CH-R£ in which Ra represents an alkyi, cycloalkyl, arylalkyl or phenyl group, characterized in that the reaction of ammonia with the diphosphine in dioxide and dihalo form of formula (Ilai) described in claim 13 and then reaction of the amino group with a compound of the type R£-CHO is performed, followed by a reduction of the diphosphine in dioxide form as described previously in either of claims 16 and 17. —'■ — • -*~~*- ^iu^ -oc i_<_ ijl v . c.. j n> u0^^-oO'v..aiii^ — ~ ^ ^J_i^J.'_*_3 v -i. - — — ,: „•.~o■' —■ .-^~■^ _n cr.c l- *"^ d ""■ ,^ TT1 r- -^ - - ■v~i --J -— _^,.^. __,-,, -, /' T "5 , ^ - _ ._ v^rt^-», — ~ -■» _n Li*C -_ olil^-- «_• uii'a - ILL* _ 'jx \ J_ ci — -\ _ _ - - —i^O^: -".-". 32. r* 3 rc "-^s f c> r or6c-fi ri"~ "^ ^~"~ 5 liJLo""~ c ~^'" J '^ — •T -v^-^'-v-^ r~* ■"■ ^3 y ~Z, -~* — ^ v- ■• —- ^i ,~* -i *~>, f- ^"> JH "-— — "^d. '-•" — .^ ^ "^ ~ -—\ -""i *-• — v —_ —- - '*•* .T Ti7 "i ^~ '"^ f~ h n W - — - — c; ■*-*. '"-• "i n r^ -* -n "' "" '" 'z " "' — 3 ""i ^ ~* "* "r"1 ^ " "^ ~ ^ v~"~ -^ ~ formula (11 =: described in claim 12 is per: crm^d; followed by a reduction of the diphosphine in dioxide form as described previously in eloner of claims 1c and 17. 33.- A pre cess for preparing one dipnospnine corresponding :: formula (1) or ' 1' ) described on one of claims 1 to 6 in which X: and X: represent an -X=X~=-;~ group, characterized in that the reaction of HM3 or MaX: with the diphesphine in dioxide and dihalo form of formula (IIa-_; described in claim 13 is performed, followed by a reduction of the diphosphine in dioxide form as described previously in either of claims 1c and 17. 34. A process for preparing one diphosphine corresponding 00 formula (i) or \Zf ) described in one of claims 1 00 6 in which X: and X2 represent a hydrocarbon-based group R chosen from alkyi, alxenyl, alkynyl, cyoloalkyl, aryl ana arylalkyl croups, characterize! in that the organomagnesium reagent corresponding to the diphosphine in dioxide and dihalo form of formula (IIa:) described in claim 13 is prepared by reacting said diphosphine with magnesium and then reaction of the reagent obtained with the halogenated hydrocarbon R-Xc (X0 = Br or CI), followed by a reduction of the diphosphine in dioxide form as described previously in either of claims 16 and 17. 35. A process for preparing the diphosphine corresponding to formula (I) or (1' ) described in one of claims 1 to 6 in which Xi and X2 represent an alkyl group substituted with one or more halogen atoms, preferably a perfluoroalkyl group, characterized in that the reaction of the diphosphine in dioxide and dihalo form of formula (Ilai) described in claim 13 with the corresponding iodo species I (CH2)pFq, in which p is between 1 and 15 and preferably between 6 and 10 and q is between 3 and 21 and preferably between 13 and 25, is performed, in the presence of copper, optionally of a base and a polar solvent. 36. A process for preparing the diphosphine corresponding to formula (1) or (I') described in one of claims 1 to 6 in which Xi and X2 represent a hydroxy1 group, characterized in that it is obtained from the diphosphine in dioxide and dihalo forjn of formula (Ilai) described in claim 13, according to an aromatic nucleophilic substitution reaction with -OH, followed by a reduction of the diphosphine in dioxide form as described previously in either cf claims 16 and 17. 37. A process for preparing the diphosphine corresponding to formula (I) or \Z' ) described in cne of claims 1 to 6 in which X: and X2 represent a group -0C0Ra in which Ra represents an alkyl, cycloalkyl, arylaikyi or phenyl group, characterized in that it is obtained by esterification of the diphosphine described in claim 36 with the carbcxylic acid RaCOOH or derivative. 38, A polymer- in racemic or optically active form, characterized in that it is obtained by reaction of a chiral or achiral diphosphine of formula (I') described in one of claims 2 to 5 with one or more polymerizable monomers. 39, The polymer as claimed in claim 38, characterized in that the diphosphine used corresponds to formula (Ia3) as follows: A* ■ kit i in said formula: - Rif ^2f Ari and Ar2 have the meaning given above in one of claims 1 to 5. 40. The polymer as claimed in either of claims 38 and 39, : characterized in that the monomer reacted with the diptiosphiin^corresponds to formula (X) below: Yi-M-Yi (X) '" inwnicn: IM,|represents a aivaient: nyarocarbpn-based group i'-bf ..^aliphatic," alicyclic and/or aromatic nature, T Yi%xepresents a functional group, preferably a carboxylic, ester, hydroxyl, amino, isocyanato, aldehyde or ketone group. 41. The polymer as claimed in claim 40, characterized in that the monomer reacted with the diphosphine corresponds to formula (X) in which M represents a Ci-C12 and preferably Ci-C6 alkylene chain; a cycloalkylene group, preferably cyclohexylene; an arylene group, preferably phenyler.e, tolylene or naphthalene. 42. A polymer in racemic or optically active form comprising the following repeating unit: in which - R: and R?, which may be identical or different, represent a hydrogen atom or a substituent, - Ar: and Ar? independently represent an alkyl, alkenyl, cycicalkyl, aryl or arylalkyl group, - M represents a divalent hydrocarbon-based group of aliphatic, alicyclic and/cr aromatic nature; - F- represents a functional orCUD resultina from the reaction: of the croup X: chosen from the following groups: aminomechyl, hydrcxyl, hydrcxymethyl, carbcxylic, ester, isocyanaco, isocyanatomethyl, . and of the group Yi chosen from carboxylic, ester, hydrcxyl, amino, isocyanato, aldehyde and V* £1 "t- f~} -*-' p. '-«■>- ,^\ - - *-, c - the degree of polymerization is preferably between 2 and 100 and oetcer still betv:een 2 and 50. 43. The polymer as claimed in claim 42, characterized in that it corresponds to the formula (P) in which M represents a C1-C3.2 and preferably Ci-C6 alkylene chain; a cycloalkylene group, preferably cyclohexylene; an ^arylene group, preferably phenylene, tolylene or naphthalene. 44, The polymer as claimed in either of claims 42 and 43, characterized in that it corresponds to the formula (P) in which Fi represents: - a urea group (Fi) resulting from the reaction of an aminomethyl group (Xi) with an isocyanato group (Yi) or an isocyanato or isocyanatomethyl group (Xi) with an amino group (Yi) , - a urethane group (Fi) resulting from the reaction of an isocyanato or ^isocyanatomethyl group (Xi) with a hydroxyl group fYi) or a hydroxyl or hydroxymethyl group; (Xi) with an isocyanato group "(Yi), - an ester group (Fi) resulting from the reaction of a carboxylic or ester group (Xx) with a hydroxyl group (Yi) or a hydroxyl or hydroxymethyl group (Xi) which a carboxylic or ester group (Yi) , - an amide Sgroup ,(Fi) resulting from the reaction of a carboxylic group (Xi) with an amino group (Yi) ror "V-fer-'-^^-^^^v^-:-. ..." •■ '."■-•:: -v..- ;--.-. ,-. ■ ■■:■:.-, :r:,]}: . an aminomethyl \group (Xi) with a carboxylic group - an ^iiuxuc^yi-uup \zu icauxcing from the reaction of ..=.■.: an^^aminpmethyl: group (Xi) with :;ah; aldehyde^.? or Ketone ^Fr6UR"i:(Yi) . " 4b. xne poxymer as claimed in one of claims 38 to 44, characterized in that the polymer is a polyurea, polyamide, polyimide, polyimine, polyester or polyurethane. 46. A process for preparing the optically active or inactive polymer described in one of claims 38 to 45, characterized in that a chiral or achiral diphosphine (I') and one or more monomers of formula (X) are polymerized. 47. The polymer as claimed in claim 42, characterized in that it is a polymer of polyurea type containing the repeating unit: in which: R: and R:, which may be identical or different, represent a hydrogen atom or a substituent, Ari and Ar2 independently represent an alkyi, alkenyl, cyclcalkyl, aryl or arylalkyl group, J represents a divalent hydrocarbon-based croup of aliphatic, alicyclic ar.d/or aromatic nature, the degree cf polymerization is preferably between 2 and IOC and barter still between 2 and 50. 48. The polymer as claimed in claim 47, characterized in that the degree cf polymerization is between 4 and 25 and preferably from 3 :o 8. 4 9. A process for preparing the polyurea as claimed in either cf claims 47 and 48, characterized in that a diphosphine bearing two -CH2-KH2 groups is polymerized with one or more di- or polyisocyanates. 50. The process as claimed in claim 49, characterized in that the diisocyanate is a diisocyanate of formula (Xa) : 0=ON-J-N=G=0 (Xa) in which: J represents a divalent hydrocarbon-based group of - aliphatic, alicyclic and/or aromatic nature, 51. The polymer as claimed in claim 42, characterized in that it is a polymer of polyamide typ§ 'containing the repeating unit: in which: '■-"--' Ri and R2, which may be identical or different, repreVeht- a hydrogen atom or a substituent, -v; > Arx^and X Ar2\ independently, represent an « alkyi, alkenyl;: cycloalkyl,, aryl or arylalkyl group, ?:-'WiIrepr^'sents a divalent hydrocarbon-based ^group H of^alapttatic, alicyclic -and/or aromatic .nature,, Athe^fd^ree: ". of polymerization is preferably ^between--2 and 100 and: better still between 2 and 50. 52. A process for preparing the polyamide as claimed in claim 51, characterized in that a diphosphine bearing two -CH2-NH2 groups is polymerized with a dicarboxylic acid. 53. The process as claimed in claim 52, characterized in that the dicarboxylic acid advantageously corresponds to formula (Xb) below: HOOC-W-COOH (Xb) in which: - W represents a divalent hydrocarbon-based group of aliphatic, alicyclic and/or aromatic nature. 54. The polymer as claimed in one of claims 9 to 12, 14 and 18, characterized in that the diphosphine corresponds to formula (I7) in which Ari and Ar2 independently represent a (C:-C6)alkyl group, a phenyl group optionally substituted with one or more (C^-Ce)alkyl or (Ci-C€)alkoxy groups; or a (C4-CP)cycloalkyl group optionally substituted with one or more (C:~ Ce)alkyl groups . 55. The polymer as claimed in claim 54, characterized in that Ara and Ar2 are identical and preferably represent phenylene and .R:„. and R2 represent a hydrogen atom. - 56. A transition metal complex comprising at least one polymer ligand as defined in one of claims 1 to 9, 38 to 45, 47, 48, 51, 54 ana 55. 57. The complex as claimed in claim 56, characterized in that the transition metal is chosen from: rhodium, ruthenium, rhenium, iridium, cobalt, nickel, platinum and palladium. 58. The use of a chiral diphosphine or of an optically active polymer as claimed in one of claims 1 to 9, 38 to 45, 47, 48, 51, 54 and 55 as a ligand for the preparation of a metal complex of a transition metal, which is useful in asymmetric catalysis. 59. The use as claimed in claim 58, characterized in that said complex is intended to catalyze the asymmetric hydrogenation of C=0, C=N or C=C bonds. 60. The use as claimed in either of claims 58 and 59, characterized in that the metal complex is a ruthenium, rhodium or iridium complex and preferably a ruthenium or rhodium complex. 61. The use of a combination of a chiral diphosphine or of an optically active polymer as claimed in one of claims 1 to 9, 38 to 45, 47, 48, 51, 54 and 55 with a diamine, for the selective reduction of ketones. 62. The use of a combination of a racemic diphosphine or of a racemic polymer as claimed in claim 58 with a chiral diamine, for the selective reduction of ketones. 63. The use as claimed in either of claims 61 and 62, characterized in that the diamine is 1,2-diamino-l,2- diphenylethane. 64. The use as claimed in claim 58 of a complex of ruthenium and of a ligand of formula (Ia3) described in claim 18 or of polymers derived therefrom, for the asymmetric catalysis of hydrogenation reactions. ■ |

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1258-chenp-2005-abstract.pdf

1258-chenp-2005-claims.pdf

1258-chenp-2005-correspondnece-others.pdf

1258-chenp-2005-correspondnece-po.pdf

1258-chenp-2005-description(complete).pdf

1258-chenp-2005-form 1.pdf

1258-chenp-2005-form 18.pdf

1258-chenp-2005-form 26.pdf

1258-chenp-2005-form 3.pdf

1258-chenp-2005-form 5.pdf

1258-chenp-2005-pct.pdf