Title of Invention	PROCESS FOR THE PREPARATION OF ALKALI METAL CYANOBORATES
Abstract	Process for the preparation of alkali metal cyanoborates of the general formula (1) M+[B(CN)4]- (1), where M is selected from the group Li, Na, K, Rb and Cs, characterized in that an alkali metal tetrafluoroborate M[BF4], where M=Li, Na, K, Rb, Cs, is reacted with an alkali metal cyanide MCN, where M=Li, Na, K, Rb, Cs, in a solid-state reaction.

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WO 2004/072089 PCT/EP2004/000231 Salts with cyanoborate anions The present invention relates to a process for the preparation of alkali metal cyanoborates, to the further conversion thereof into salts comprising cyanoborate anions and organic cations, to these salts, and to the use thereof as ionic liquids. Ionic liquids or liquid salts are ionic species which consist of an organic cation and a generally inorganic anion. They do not contain neutral molecules, and generally have melting points below 373 K. A multiplicity of compounds which are used as ionic liquids are known in the prior art. In particular, they are also the Subject-mat" ter of a series of patents and patent applications. Thus, solvent-free ionic liquids were disclosed for the first time by Hurley and Wier in a series of US patents (US 2,446,331, US 2,446,339 and US 2,446,350). These "salts which are molten at room temperature" comprised AICI3 and a multiplicity of n-alkylpyridinium halides. In recent years, some review articles have been published on this topic (R. Sheldon "Catalytic reactions in ionic liquids", Chem. Commun., 2001, 2399- 2407; M.J. Earle, K.R. Seddon "Ionic liquids. Green solvent for the future", Pure Appl. Chem., 72 (2000), 1391-1398; P. Wasserscheid, W. Keim "lonische Flussig- keiten - neue Lösungen fur die Übergangsmetallkatalyse" [Ionic Liquids - Novel Solutions for Transition-Metal Catalysis], Angew. Chem., 112 (2000), 3926-3945; T. Welton "Room temperature ionic liquids. Solvents for synthesis and catalysis", Chem. Rev., 92 (1999), 2071-2083; R. Hagiwara, Ya. Ito "Room temperature ionic liquids of alkylimidazolium cations and fluoroanions", Journal of Fluorine Chem., 105 (2000), 221-227). The properties of ionic liquids, for example melting point, thermal and electro- chemical stability, viscosity, are greatly influenced by the nature of the anion. By contrast, the polarity and hydrophilicity or lipophilicity can be varied through a suit- able choice of the cation/anion pair. There is therefore a basic demand for novel ionic liquids having varied properties which facilitate additional possibilities with respect to their use. Crucial advances in the area of ionic liquids have been achieved with the discov- ery of 1-ethyl-3-methylimidazolium chloroaluminate. This salt has a broad liquid WO 2004/072089 PCT/EP2004/000231 -2- range and an electrochemical window of greater than 3 V and is thus of great interest for electrochemical and synthetic purposes. However, its use is limited by the chemical instability, especially to moisture. After the discovery of the more hydrolysis-stable 1-ethy!-3-methylimidazolium tetrafluoroborate, combinations of alkylimidazolium cations with inorganic or organic anions were investigated, of which 1 -ethyl-3-methyiimidazoiium tetrafluoroborate is the best characterised. The stability of the imidazolium cation is relatively high and its decomposition tem- perature is essentially determined by the anion. Thus, 1-ethyl-3-methylimidazolium salts with triflate and bis(trifluoromethylsulfonyl)imide anions are stable UD to 400°C, whereas 1-ehy|-3-methilimidazolium tetrafluoroborate is only stable up to The prior art describes borate anions in which fluorine ligands have been replaced by cyanide (E. Bernhardt, G. Henkel, H. Willner, Z Anorg. Allg. Chem. 626 (2000) 560; D. Williams, B. Pleune, J. Kouvetakis, M. D. Williams, R. A. Andersen, J. Amer. Chem. Soc. 122 (2000) 7735; E. Bernhardt, M. Berkei, M. Schurmann, H. Willner, Z Anorg. Allg. Chem. 628 (2002) 1734) and trifluoromethyl ligands (E. Bernhardt, G. Henkel, H. Willner, G. Pawelke, H. Burger, Chem. Eur. J. 7 (2001) 4696; G. Pawelke, H. Burger, Coord. Chem. Rev. 215 (2001) 243). The trifluoro- methyl borates are synthesised here starting from the cyanoborates, but the cyanoborates are only accessible with difficulty and in small amounts. The synthe- sis of [B(CN4)] is labour-intensive and can only be carried out on a small prepara- tive scale. In addition, the starting materials are expensive. The object of the present invention is to provide novel stable compounds having valuable properties which can be used as ionic liquids, and a process for the preparation thereof. In particular, the object is to provide salts with borate anions which have higher stability than the salts with tetrafluoroborate anions. A further object of the present invention is to provide an effective and economical process for the preparation of these borate salts and their precursors. This object is achieved in accordance with the invention by the characterising features of the main claim and the sub-claims. WO 2004/072089 PCT/EP2004/000231 -3- The present invention therefore relates firstly to a process for the preparation of alkali metal cyanoborates of the general formula (1) M+ [B(CN)4]- (1). where M is selected from the group Li, Na, K, Rb and Cs, in which the readily available starting substances alkali metal tetrafluoroborate M[BF4] (M = Li, Na, K, Rb, Cs) and alkali metal cyanide MCN (M = Li, Na, K, Rb, Cs) are reacted with one another in a solid-state reaction. The alkali metal tetrafluoroborate used in accordance with the invention is prefera- bly potassium tetrafluoroborate K[BF4] or sodium tetrafluoroborate Na[BF4], and the alkali metal cyanide used in accordance with the invention is preferably potas- sium cyanide KCN or sodium cyanide NaCN. In a preferred variant of the process according to the invention, the alkali metal tetrafluoroborate is reacted with the alkali metal cyanide in the presence of a lith- ium halide. The lithium halide here is selected from LiCI, LiBr and Lil, it is particu- larly preferably lithium chloride LiCI. Alkali metal cyanide and lithium halide can in each case be employed in an excess of one of the two reagents. However, the alkali metal cyanide and the lithium hal- ide are preferably brought to reaction in approximately in the molar ratio 1:1. The alkali metal tetrafluoroborate and the alkali metal cyanide are preferably employed in the molar ratio of 1:4 to 1:12, particularly preferably in the molar ratio of about 1:9. The alkali metal tetrafluoroborate: alkali metal cyanide : lithium halide molar ratio of about 1:9:9 is therefore very particularly preferably used. The starting materials used for the reaction according to the invention are particu- larly preferably potassium tetrafluoroborate K[BF4] as alkali metal tetrafluoroborate and potassium cyanide KCN as alkali metal cyanide. The solid-state reaction according to the invent/on is carried out at temperatures between 100°C and 500°C. Preference is given to temperatures of 250 to 400°C, particularly preferably 280 - 340°C. WO 2004/072089 PCT/EP2004/000231 -4- Without restricting generality, the subject-matter of the solid-state reaction according to the invention is explained with reference to a general example: K[BF4], KCN and LiCI are mixed in the molar ratio of 1:9:9 and subsequently brought to reaction in the melt. The reaction temperature is selected in such a way that on the one hand the KCN/LiCI mixture forms a eutectic melting at 270 - 290°C and on the other hand the tetracyanoborate salts formed only decompose slowly ( with LiCI (molar ratio 1:1) enables mixed crystals of the K(CI,CN) type (a = 6.34 A, F m3m) and a further unidentified compound (d = 4.958,2.878, 2.728, 2.482, 2.175 A) to be detected. The yield of K[B(CN)4] is virtually temperature-independ- ent in (tie range 280 - 340°C and is about 10 - 601 based on TO. It is found in fyrther experiment that a reduction in the molar ratio of K(BF4] to KCN/LiCi from 1:9 to 1:4.5 results in reductions in yield. The Raman spectra of the reaction mix- tures show that the tetracyanoborate is in the form of the lithium salt after the reaction (v(CN) =2263 cm-1). In the analogous reaction using an NaCN/LiCI mixture, mixed crystals of the (Li,Na)(CI,GN) type (a = 5.50A Fm3m) form in the melt of NaCN with LiCI (molar ratio 1:1) besides a little LiCN (d= 5.216, 3.626 A, m.p. 160°C). A eutectic (120-140°C) forms between NaCN with LiCI, in contrast to KCN/LiCI, but the mixed crystals only melt at 360 - 540°C; this is probably the eause of the lower yields (about 25%) of Na[B(CN)4]. During work-up of the reaction products, the excess cyanide must firstly be des- _ troyed. It is found that oxidation of the cyanide using aqueous 30% H2O2 solution is the best work-up method. The low salt burden and the complete and rapid degradation of the cyanide remaining in the reaction mixture, as well as the good yields outweigh the single disadvantage, the often vigorous and difficult-to-control reaction of the cyanide. The tetracyanoborate is subsequently extracted from the aqueous solution and converted into the K or Na salt by re-extraction. An alternative method available for the work-up of the solid-state reaction products is oxidation of the unreacted cyanide using aqueous NaOCI solution, which pro- ceeds within a few minutes under very mild conditions, i.e. without warming or foaming of the reaction mixture. The work-up is then carried out analogously to that with H2O2. However, this further work-up is more labour-intensive and time- consuming owing to the greater salt burden. WO 2004/072089 PCT/EP2004/000231 -5- The present invention furthermore relates to a process for the preparation of alkali metal cyanoborates of the general formula (2) M+ [BFn(CN)4-n]- (2), where n = 0,1,2 or 3 and M is selected from thG group Li, Na, K, Rb and Cs, in which an alkali metal cyanide MCN, where M = Li, Na, K, Rb, Cs, is reacted with boron trifluoride etherate BF3 OET2 On use of coarse-grained potassium cyanide KCN and BF3-OEt2, equimolar amounts of K[BF4] and K[BF2(CN)2] also form in the reaction according to the invention alongside the primary adduct K[BF3(CN)], in accordance with the follow- ing equations: K[BF3(CN)] + BF3-OEt2 → K[BF4] + BF2(CN)-OEt2 BF2(CN)-OEt2 + KCN → K[BF2(CN)2] + Et2O In addition, the two salts K[BF(CN)3] and K[B(CN)4] form to a lesser extent, the former in particular if the reaction mixture is held at temperatures above room temperature. In accordance with the invention, the boron trifluoride etherate is reacted with the alkali metal cyanide in the presence of an aprotic solvent. Without restricting gen- erality, the aprotic solvent can be, for example, acetonitrile, diethyl ether, tetra- hydrofuran and/or dimethoxyethane. The alkali metal cyanide used for the process according to the invention is pref- erably potassium cyanide KCN. The starting materials are preferably reacted in accordance with the invention at temperatures of-80 to 100°C, particularly preferably at room temperature. WO 2004/072089 PCT/EP2004/000231 -6- Volatile by-products which are removed under reduced pressure may be formed during the reaction. Mostly, however, by-products which are insoluble in the sol- vents used and are separated off by filtration form. The solvent is, if desired, removed under reduced pressure together with volatile by-products, and the alkali metal cyanoborates obtained can, if desired, be separated and purified by a com- mon possibility known to the person skilled in the art. A third and fourth subject-matter of the present invention are a process for the preparation of salts with cyanoborate anions of the general formula (3) and the corresponding salts of the general formula (3) ktf |BFn(CN)4-n] (3), where n = 0,1,2 or 3, and Kt+ is an organic cation, with the proviso that the cation Kt+ is not [N(C4H9)4]+ for n=0. For the preparation of the salts, an alkali metal cyanoborate of the general formula M+ [B(CN)4]-, where M is selected from the group Li, Na, K, Rb and Cs, or an alkali metal cyanoborate of the general formula M+ [BFn(CN)4-n]-, where n = 0,1,2 or 3 and M is selected from the group Li, Na, K, Rb and Cs, is reacted with Kt+ X-, where X is a halogen selected from Cl, Br and I, and Kt+ is an organic cation, with the proviso that the cation Kt+ is not [N(C4H9)4]- for n=0. where R = H, with the proviso that at least one R on the hetero atom is different from H, straight-chain or branched alkyl having 1-20 carbon atoms straight-chain or branched alkenyl having 2-20 carbon atoms and one or more double bonds straight-chain or branched alkynyl having 2-20 carbon atoms and one or more triple bonds WO 2004/072089 PCT/EP2004/000231 -7- saturated, partially or fully unsaturated cycloalkyl having 3-7 carbon atoms halogen, in particular fluorine or chlorine, with the proviso that no halogen-hetero atom bond is present, -NO2, with the proviso that no bond to a positively charged hetero atom is present, and at least one R is different from NO2, -CN, with the proviso that no bond to a positively charged hetero atom is present, and at least one R is different from CN, where the R are in each case identical or different, where the R may be bonded to one another in pairs by single or double bond, where one or more R may be partially or fully substituted by halogens, in particular -F and/or -Cl, or partially by -CN or -NO2, with the proviso that not all R are fully halogenated, and where one or two carbon atoms of the R may be replaced by hetero atoms and/or atom groups selected from the group -O-, -C(O)-, C(O)O-, -S-, -S(O)-, -SO2-, -S(O)2O-, -N= -P=, -NR'-, -PR'-, -P(O)(OR)-, -P-(O)(OR')O-, -P(O)(NR'R')-, -P(O)(NR'R')O-, -P(O)(NR'R')NR'-, -S(O)NR'- and -S(O)2NR'-, where R' = H, non-, partially or perfluorinated C1- to C6-alkyl or non-, partially or perfluorinated phenyl. For the purposes of the present invention, fully unsaturated substituents are also taken to mean aromatic substituents. Besides hydrogen, suitable substituents R of the organic cation in accordance with the invention are: C1- to C20-, in particular C1- to C-12-alkyl groups, C2- to C20-, in particular C2- to C12-, alkenyl or alkynyl groups, saturated or unsaturated, i.e. also aromatic, C3- to C7-cycloalkyl groups, NO2, CN or halogens. However, a restricting factor for the halogens here is that they only occur as substituents on carbon atoms, but not on hetero atoms. NO2 and CN do not occur as substituents of a WO 2004/072089 PCT/EP2004/000231 -8- positively charged hetero atom; furthermore, not all substituents simultaneously have the meaning of NO2 or CN. The substituents R may also be bonded in pairs in such a way that cyclic, bi- or polycyclic cations are formed. The substituents may be partially or fully substituted by halogen atoms, in particular by F and/or Cl, or partially by CN or NO2 and con- tain one or two hetero atoms or atom groups, selected from the group 0, (O), C(O)O, S, S(O), SO2) SO2O, N, P, NH, PH, NR', PR', P(O)(OR'), P(O)(OR')O, P(O)(NR'R'), PP)(NR'R')O, P(O)(NR'R')NR', S(O)NR' and S(O)2NR'. In the case of complete halogenation, however, not all substituents R present may be fully lialogenated, i.e. at least one R is not perhalogenated. Without restricting generality, examples of substituents according to the invention of the organic cation are: -F, -Cl, -Br, -I, -CH3, -C2H5, -C3H7, -CH(CH3)2, -C4H9, -C(CH3)3, -C5H11, -C6H13, -C6H13, -C7H15, -C8H17, -C9H19, -C10H21, -C12H25,-C20H41, -OCH3, -OCH(CH3)2, -CH2OCH3, -C2H4OCH(CH3)2, -SCH3, -SCH(CH3)2, -C2H4SC2H5, -C2H4SCH(CH3)2, -S(O)CH3, -SO2CH3, -SO2C2H5, -SO2C3H7, -SO2CH(CH3)2-CH2SO2CH3, -OSO2CH3, -OSO2CF3, -CH2N(H)C2H5, -C2H4N(H)C2H5, -CH2N(CH3)CH3, -C2H4N(CH3)CH3, -N(CH3)2, -N(CH3)C3H5l --N(CH3)CF3, O-C4H8-O-C4H9, -S-C2H4-N(C4H9)2, -OCF3, -S(O)CF3, -SO2CF3, -CF3, -C2F5> -C3F7, -C4F9, -C(CF3)3, -CF2SO2CF3, -C2F4N(C2F5)C2F5, -CF=CF2, -C(CF3)=CFCF3, -CF2CF=CFCF3, -CF=CFN(CF3)CF3, -CFH2, -CHF2> -CH2CF3, -C2F2H3, -C3FH6l -CH2C3F7, -C(CFH2)3, -CHO, -C(O)OH, -CH2C(O)OH, -CH2C(O)CH3, -CH2C(O)C2H5, -CH2C(O)OCH3, CH2C(O)OC2H5, -C(O)CH3, -C(O)OCH3, WO 2004/072089 PCT/EP2004/000231 -9- Without restricting generality, the following organic cations are particularly pre- ferred as salts according to the invention: The salts according to the invention are advantageously very readily soluble in organic solvents. In comparison to known liquid salts, the salts according to the invention surprisingly have low viscosity. The salts according to the invention are advantageously stable. They can be isolated and stored at room temperature. Furthermore, the salts according to the invention are relatively easy to prepare, and readily available starting materials are required. All compounds according to the invention and compounds of the formula [N(C4H9)4]+ [B(CN)4]~ have a salt-like character, relatively low melting points (usu- ally below 100°C) and can be used as ionic liquids. The salts according to the invention and salts of the formula [N(C4H9)4]+ [B(CN)4]- can be employed as solvents for many synthetic or catalytic reactions, for example Friedel-Crafts acylation and alkylation, Diels-Alder cycloadditions, hydrogenation WO 2004/072089 PCT/EP2004/000231 -10- and oxidation reactions, Heck reactions. Furthermore, for example, fluorinated sol- vents for secondary and primary batteries can be synthesised. The salts according to the invention and salts of the formula [N(C4H9)4]+ [B(CN)4]- are suitable as precursors for the preparation of liquid-crystal compounds and of active ingredients, inter alia for medicaments and crop-protection agents. It is also possible to use the compounds according to the invention and the salts of the formula [N(C4H9)4]+ [B(CN)4]- as non-aqueous electrolyte, optionally in combi- nation with other electrolytes known to the person skilled in the art. In addition, the salts according to the invention and salts of the formula [N(C4H9)4]+ [B(CN)4]- are of interest as non-aqueous, polar substances in suitable reactions as phase-transfer catalyst or as medium for the heterogenisation of homogeneous catalysts. The complete disclosure content of all applications, patents and publications men- tioned above and below are incorporated into this application by way of reference. Even without further comments, it is assumed that a person skilled in the art will be able to utilise the above description in the broadest scope. The preferred embodi- ments and examples should therefore merely be regarded as descriptive disclo- sure which is absolutely not limiting in any way. The NMR spectra were measured on solutions in deuterated solvents at 20°C in a Bruker Avance DRX-300 spectrometer with a 5 mm 1H/BB broad-band head with deuterium lock. The measurement frequencies of the various nuclei are: 1H: 300.13 MHz, 11B: 96.92 MHz, 13C: 75.47 MHz, 19F: 282.41 MHz and 15N: 30.41 MHz. The referencing method is indicated separately for each spectrum or each data set. DSC measurements were carried out in a Netzsch DSC 204 instrument. The tem- perature and sensitivity were calibrated using naphthalene, benzoic acid, KNO3, AgNO3, LiNO3 and CsCI. In each case, 5-20 mg of the substances were weighed out into an aluminium crucible and sealed with aluminium caps with a small aper- ture. The investigation was carried out in the temperature range from 25 to 500°C. Unless indicated otherwise, the heating rate is 10 Kmin-1. During the measure- WO 2004/072089 PCT/EP2004/000231 -11- ment, the sample space was flushed with dry nitrogen. The samples of air-sensi- tive substances were prepared in a dry box and transported to the analytical instrument in an argon-filled vial. The data evaluation was carried out using the Netzsch Protens 4.0 program. The elemental analyses were carried out by the microanalysis combustion meth- ods using a Euro EA3000 from HEKA-Tech GmbH. The samples of air-sensitive substances Were prepared !n a dry box and transported to the analytical instru- ment in an argon-filled vial. The error limits for the recorded atoms are: C:±0.3%, H:±0.1%,:N±o.2% WO 2004/072089 PCT/EP2004/000231 -12- Example 1: Synthesis of K[B(CN)4] KCN, LiCI and K[BF4] are ground coarsely and mixed with one another in a mortar in a dry box (MBraun, Munich). The mixture is finely ground using a commercially available coffee grinder. The reaction mixture is subsequently transferred into a nickel crucible (Øinternal = 101 mm, dwal = 2 mm, h = 85 mm). The crucible is cov- ered loosely by an iron lid, transferred from the dry box into a muffle furnace (VMK 93, Kontron Material und Strukturanalyse GmbH) and heated. When the reaction is complete, the crucible with the metal cover is removed from the still hot muffle furnace and cooled to room temperature in air. The cooled grey/black porous reaction mixture is transferred out of the crucible into a mortar and crushed coarsely. 150 ml of water are subsequently added to the comminuted solid in a 3 I beaker, and a total of 350 ml of H2O2 (30% aqueous solution, about 3 mol) are added in approximately 30 ml portions over a period of half an hour with constant stirring. The reaction, which commences exothermically with vigorous evolution of gas, is controlled by addition of ice. The reaction mixture (V= 2.3 I) is divided between two 3 I beakers and acidified using concentrated HCI . (about 300 ml, about 3.6 mol) (pH 5-7) until gas evolution is no longer observed. It is subsequently checked whether cyanide residues are still present in the mix- ture (cyanide test, Merck KGaA, Darmstadt, Germany). The mixture is then fil- tered, and 28 ml (0.34 mol) of cone. HCI are added to the yellow solution with stir- ring. 47 g (63 ml, 0.33 mol) of tripropylamine are subsequently added. The reac- tion mixture is stirred for 15 minutes and extracted with dichloromethane (250,150 and 50 ml). The combined organic phases are washed with 200 ml of H2O, and the washings are re-extracted with 25 ml of dichloromethane. The combined di- chloromethane phases are dried over MgSO4 and filtered through a glass frit (D4). 35 g (0.63 mol) of KOH are dissolved in a little water and added to the organic solution with vigorous stirring. A beige oily substance immediately precipitates out and forms lumps on the vessel base after further stirring (30 min). The dichloro- methane/tripropylamine mixture is decanted off, and the product is extracted from the residue with THF (200,100 and 50 ml). The collected THF phases are dried using K2CO3, and finally all volatile constituents are removed in a rotary evapora- tor. The white product is washed with dichloromethane and dried at room tem- perature under reduced pressure. WO 2004/072089 PCT/EP2004/000231 -13- [a] Oxidation of the unreacted CN" using H2O2. [b] Oxidation of the unreacted CN' using NaOCI. 13C{1H}-NMR: δ = 123.3 ppm (q, 4C, CN), 1Δ13C(10/11B) = 0.0021 ppm, 1J(11B,13C) = 70.9 Hz; 11B-NMR: δ = -38.6 ppm, V(11B,13C) = 71.2 Hz; solvent: CD3CN reference substances: 13C-NMR solvent peak (against TMS) and 11B-NMR BF3Et2O/CD3CN as external standard. The NMR data are identical with those in the prior art (E. Bernhardt, G. Henkel, H. ■- Willner, Z Anorg. Allg. Chem. 626 (2000) 560). Results of the elemental analysis : According to DSC measurements, the salt decomposes above 450°C. Example 2: Synthesis of Na[B(CN)4] 170.3 g (2.62 mol) of KCN, 116.1 g (2.74 mol) of LiCI and 37.2 g (0.30 mol) of K[BF4] are weighed out, ground coarsely in a mortar and mixed with one another. The further procedure corresponds to that described under Example 1 (reaction WO 2004/072089 PCT/EP2004/000231 -14- temperature 300°C, reaction time 1.5 hours) as far as the obtaining of the dichloromethane extract. 2 equivalents of NaOH (about 25 g, 0.63 mol) are dissolved in as little water as possible (aboui 10-20 ml) and added dropwise to the organic solution with vigor- ous stirring. A beige oily substance immediately precipitates out and forms lumps on the vessel basG after further stirring (at least 30 min). The dichloromethane/ tripropylamine mixture is decanted off, and the product IS extracted from the resi- due with THF (200 ml, 100 ml and 50 ml). If the beige residue becomes liquid due to the extraction, its viscous consistency can be restored by careful addition of Na2CO3 or Na2SO4. The collected THF phases are dried using Na2CO3 or Na2SO4, and finally all vola- tile constituents are removed in a rotary evaporator. The white product is washed with dichloromethane in order to remove amine residues and dried at 60°C under reduced pressure. Yield 25.3 g (62%, 0.18 mol). 13C{1H}-NMR: δ = 123.3 ppm (q, 4C, CN), M13C(10/11B) = 0.0021 ppm, 1J(11B,13C) = 70.9 Hz; 11B-NMR: δ = -38.6 ppm, 1J(11B,13C) = 71.2 Hz; solvent: CD3CN reference substances: 13C-NMR solvent peak (against TMS) and 11B-NMR BF3Et2O/CD3CN as external standard The NMR data are identical with those in the prior all (E. Bernhardt, G. Henkel, H. Willner, Z. Anorg. Allg. Chem. 626 (2000) 560). Results ofihe elemental analysis : Example 3: Lithium tetracyanoborate, Li[B(CN)4] 5 g (32 mmol) of K[B(CN)4] are dissolved in 20 ml of water and reacted with 8 ml of 37% hydrochloric acid (96 mmol) and 8 ml of "Pr3N (42 mmol). This mixture is then extracted twice with 50 ml of CH2CI2 each time, the organic phase is dried using MgSO4, and a solution of 3 g of LiOH-H2O (72 mmol) in 20 ml of water is added, and the mixture is stirred vigorously for one hour. All volatile products are removed under reduced pressure. Li[B(CN)4] is extracted from the residue with 50 ml of WO 2004/072089 PCT/EP2004/000231 -15- CH3CN in a Soxlett apparatus. The organic phase is evaporated in a rotary evapo- rator. The crude product is recrystallised from water, washed with 50 ml of CH2CI2 and freed from solvent residues under reduced pressure. Yield 3.5 g (80%, 29 mmol). According to DSC measurements, the salt decomposes above 470°C. Example 4: Ammonium tetracyanoborate, NH4[B(CN)4] 0.31 g (2.0 mmol) of K[B(CN)4] are dissolved in 8 ml of water, then reacted with a solution of 0.20 g (1.1 mmol) of (NH4)2[SiF6] in 8 ml of water. All volatile constitu- ents are removed under reduced pressure. NH4[B(CN)4]is extracted from the resi- due With 10 ml Of CH3CN. The organic phase is evaporated in a rotary evaporator. The crude product is washed with 10 ml of CH2CI2 and dried under reduced pres- sure. Yield 0.25 g (93%, 1.9 mmol). According to DSC measurements, the salt decomposes above 300°C. Example 5: Trityl tetracyanoborate, [Ph3C][B(CN)4] 500 mg (2.3 mmol) of Ag[B(CN)4] and 726 mg (2.3 mmol) of (C6H5)3CBr in anhy- drous acetonitrile are brought to reaction in a 250 ml glass flask with PTFE valve (Young, London). The acetonitrile is removed under reduced pressure after 4 hrs, and 100 ml of dichloromethane are subsequently added. The suspension is filtered through a Celite®-covered frit in a Schlenk flask. The reaction flask is rinsed twice with dichloromethane (20 ml and 10 ml). The solution is evaporated to 10 ml under reduced pressure, and, after addition of 70 ml of anhydrous hexane, an orange solid precipitates out. This is filtered off via a Schlenk frit and rinsed with a further 10 ml of hexane. The orange [Ph3C][B(CN)4] is dried under reduced pressure and stored in a dry box. The yield is 408 mg (51%, 1.3 mmol). 1H-NMR: δ = 7.73 ppm (m, 6H, o-H), δ = 7.94 ppm (m, 6H, m-H), 5 = 8.31 ppm (tt, 3H, p-H); 13C{1H}-NMR: δ = 122.7 ppm (q, 4C, CN), 1J(11B,13C) = 71.5 Hz, 6 = 131.0 ppm (s, 6C, m-C), δ = 140.2 ppm (s, 3C, i-C), 6 = 143.0 ppm (s, 6C, o-C), δ = 143.8 ppm (s, 3C,p-C), δ = 211.2 ppm (s, 1C, C+); 11B-NMR: WO 2004/072089 PCT/EP2004/000231 -16- δ = -38.6 ppm, V(11B,13C) = 71.3 Hz; solvent: CDCI3 reference substances: 1H- and 13C-NMR solvent signal (against TMS) and 11B-NMR BF3.Et2O/CD3CN as external standard [Ph3C][B(CN)4] melts at 158°C with decomposition. Example 6: [HNPhMe2][B(CN)4] 1.50 g (9.7 mmol) of K[B(CN)4] are dissolved in 50 ml of water. Firstly 3 ml (36 mmol) of cone. HCI solution and subsequently 1.23 ml (9.7 mmol) of N,N-di- methylaniline are added to the solution with stirring, whereupon a white solid pre- cipitates out. The solution is extracted twice with dichloromethane (100 ml and 30 ml), the organic phase is dried using MgSO4, and the dichloromethane is removed under reduced pressure, giving white [HNPhMe2][B(CN)4], which is puri- fied by washing with pentane. Yield 2.12 g (92%, 8.9 mmol). 1H-NMR: δ = 3.23 ppm (s, 6H, CH3), M1H(12/13C) = -0.0023, 1J(1H,13C) = 145.48 Hz, δ = 7.64-7.58 ppm (m, 5H, C6H5); 13C{1H}-NMR: δ = 47.8 ppm (s, 2C, CH3), δ = 121.5 ppm (s, 2C, C6H5), δ= 123.2 ppm (s, 4C, CN), 1J(11B,13C) = 71.3 Hz, V3C(10/11B) = -0.0020 ppm, δ = 131.5 ppm (s, 2C, C6H5), δ= 131.6 ppm (s, 1C, C6H5), δ= 143.1 ppm (s, 1C, C6H5); 11B-NMR: δ = -38.6 ppm, V(11B,13C) = 71.3 Hz; 15N-NMR: δ = -103.2 ppm (q, 4N, CN), V(11B,15N) = 0.73 Hz; solvent: CD3CN; reference substances: 1H- and 13C-NMR solvent signal (against TMS), 11B-NMR BF3Et2O/CD3CN as external standard and 15N-NMR 80% of CH3NO2 in CD3CN as external standard. Results of the elemental analysis of [HNPhMe2][B(CN)4]: WO 2004/072089 PCT/EP2004/000231 -18- water (20 ml) and dried using MgSO4, and the dichloromethane is subsequently removed under reduced pressure. Yield 0.50 g (87%, 2.0 mmol). Results of the elemental analysis of [C8H15N2][B(CN)4]: [C8H15N2][B(CN)4] melts below -50°C and decomposes endothermically above 410°C. Example 9: 1-Ethyl-3-methylimidazolium tetracyanoborate [C6H11N2][B(CN)4] [C6H11N2][B(CN)4] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C6H11N2][B(CN)4]: [C6H11N2][B(CN)4] melts below-50°C and decomposes endothermically above 420°C. Example 10: p-Methylbutylpyridinium tetracyanoborate [C10H16N][B(CN)4] [C10H16N][B(CN)4] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C10H16N][B(CN)4]: PCT/EP2004/000231 WO 2004/072089 -19- [C10H16N][B(CN)4] solidifies at-25°C, melts at 42°C and decomposes endothermic- ally above 390°C. Example 11: Preparation of K[BF2(CN)2] Variant A: 5.88 g (41 mmol) of BF3-OEt2 and 30 ml of CH3CN are condensed onto 4.12 g (63 mmol) of KCN in a 50 ml flask with PTFE valve. The reaction mixture is stirred at room temperature for 3 h, and all volatile constituents are subsequently removed under reduced pressure, and the residue is dissolved in about 50 ml of CH3CN and freed from KCN and K[BF41 by filtration. After removal of the aceto- nitrile under reduced pressure, 2.66 g (19 mmol) of K[BF2(CN)2] (11B- and 19F- NMR: 93% of [BF2(CN)2]', 0.3% of [BF3(CN)]- and about 7% of unknown species) are obtained. Yield: 92%. Pure colourless K[BF2(CN)2] is obtained by recrystaflisa- tion from water. Isolated yield: 2.08 g (72%, 15 mmol). Variant B: 65 g (1.0 mol) of KCN and 200 ml of CH3CN are initially introduced in a 500 ml round-bottomed flask with dropping funnel. 50 ml (56 g, 0.4 mol) of BF3OEt2 are added dropwise over the course of half an hour with stirring at room temperature. During the addition, the temperature rises to 50°C. After further stir- ring (1.5 h) at room temperature, the solution is filtered off, and the filter residue (KCN and K[BF4]) is washed with about 300 ml of CH3CN. The combined aceto- nitrile phases are evaporated in a rotary evaporator, giving 20 g of impure K[BF2(CN)2] as crude product. The crude product is reacted with 30 ml of cone. HCI and 35 ml (25 g, 170 mmol) of tripropylamine in 200 ml of water and extracted as tripropylammonium salt with 200 ml of dichloromethane. The dichloromethane phase is dried using MgSO4 and reacted with vigorous stirring with 25 g of KOH dissolved in as little water as possible. The viscous aqueous phase is separated off and washed with dichloromethane. The product is extracted from the residue with about 300 ml of CH3CN, and the solution is dried using K2CO3 and evapo- rated in a rotary evaporator. The white product is washed with dichloromethane and dried under reduced pressure. Yield: 17 g (60%, 120 mmol). According to 11B-NMR, the substance contains 98% of [BF2(CN)2]". WO 2004/072089 PCT/EP2004/000231 -20- Example 12:1-Ethyl-3-methylimidazolium tricyanofluoroborate [C6H11N2][BF(CN)3] [C6HiiN2][BF(CN)3] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C6H11N2][BF(CN)3]: C[%3 H[%] N[%] theoretical 49.35 5.06 31.98 found 48.52 4.84 31.20 [C6H11N2][BF (CN)3] is liquid it room temperature. Example 13:1-Butyl-3-methylimidazolium tricyanofluoroborate [C8H15N2][BF(CN)3] [C8H15N2][BF(CN)3] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C8H15N2][BF(CN)3]: C [%] H [%] N [%] theoretical 53.47 6.12 28.34 found 54.06 6.09 28.68 [C8H15N2][BF(CN)3] melts below -50°C and decomposes exothermically above 300°C. Example 14: p-Methylbutylpyridinium tricyanofluoroborate [C10H16N][BF(CN)3] [C10H16N][BF(CN)3] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C10H16N][BF(CN)3]: C [%] H [%] N [%] theoretical 60.50 6.25 21.71 found 61.13 5.51 22.35 WO 2004/072089 FCT/EF2004/000231 -21- [C10H16N][BF(CN)3] melts below -50°C and decomposes exothermically above 260°C. Example 15:1-Ethyl-3-methylimidazolium dicyanodifluoroborate [C6H11N2][BF2(CN)2] [C6H11N2][BF2(CN)2] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C6H11N2][BF2(CN)2]: [C6H11N2][BF2(CN)2] melts below-50°C and decomposes exothermically above 200°C. Example 16:1-Butyl-3-methylimidazolium dicyanodifluoroborate [C8H15N2][BF2(CN)2] [C8H15N2][BF2(CN)2] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C8H15N2][BF2(CN)2]: [C8H15N2][BF2(CN)2] melts below -50°C and decomposes exothermically above 210°C. WO 2004/072089 PCT/EP2004/000231 -22- Example 17: p-Methylbutylpyridinium dicyanodifluoroborate [C10H16N][BF2(CN)2] [C10H16N][BF2(CN)2] is prepared analogously to [C8H15N2][B(CN)4] with the same yield. Results of the elemental analysis of [C10H16N][BF2(CN)2]: [C10H16N][BF2(CN)2] melts below -50°C and decomposes exothermically above 190°C. -23- WE CLAIM; 1. Process for the preparation of alkali metal cyanoborates of the general formula (1) M+[B(CN)4] (1), where M is selected from the group Li, Na, K, Rb and Cs, characterized in that an alkali metal tetrafluoroborate M[BF4], where M=Li, Na, K, Rb, Cs, is reacted with an alkali metal cyanide MCN, where M=Li, Na, K, Rb, Cs, in a solid- state reaction. 2. Process as claimed in claim 1, wherein the alkali metal tetrafluoroborate is K[BF4] or Na[BF4] and in that the alkali metal cyanide is KCN or NaCN. 3. Process as claimed in claim 1 or 2, wherein the alkali metal tetrafluoroborate is reacted with the alkali metal cyanide in the presence of a lithium halide selected from LiCI, LiBr and Lil, preferably in the presence of LiCI. 4. Process as claimed in claim 3, wherein the alkali metal cyanide and the lithium halide are employed in the molar ratio 1:1. -24- 5. Process as claimed in one or more of claims 1 to 4, wherein the alkali metal tetrafluoroborate and the alkali metal cyanide are employed in tne molar ratio from 1:4 to 1:12, preferably in the molar ratio 1:9. 6. Process as claimed in one or more of claims 1 to 5, wherein the alkali metal tetrafluoroborate employed is K[BF4] and the alkali metal cyanide employed is KCN. 7. Process as claimed in one or more of claims 1 to 6, wherein the reaction is carried out at temperatures between 100°C and 500°C, preferably at 250- 400°C, particularly preferably at 280-340°C. Process for the preparation of alkali metal cyanoborates of the general formula (1) M+[B(CN)4]- (1), where M is selected from the group Li, Na, K, Rb and Cs, characterized in that an alkali metal tetrafluoroborate M[BF4], where M=Li, Na, K, Rb, Cs, is reacted with an alkali metal cyanide MCN, where M=Li, Na, K, Rb, Cs, in a solid-state reaction.

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