Title of Invention

"A PROCESS FOR THE PREPARATION OF NOVEL REUSABLE HETEROGENEOUS NANOPALLADIUM (O) CATALYST"

Abstract

The present invention relates to A process for the preparation of a reusable heterogeneous nanopalladium(O) catalyst. The catalyst on the solid support perform C-C bond formation reactions such as Heck, Suzuki, Sonagashira, and Stille type reactions of haloarenes that include unreactive chloroarenes. Heterogeneous nanopalladium(O) catalysts are prepared by an exchange of PdC142- " on the support selected from LDH and S'-NR3X wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl , X is selected from the group consisting of C1, Br, I, F, OH and OAc in an aqueous solvent at a temperature ranging between 20 to 30 °C for a period ranging from 5 to 24 h under nitrogen atmosphere followed by filtration and reduction with hydrazine hydrate in ethanol at room temperature . Filtration gave the desired nanopalladium(O) catalysts.

Full Text

The present invention relates to A process for the preparation of a reusable heterogeneous nanopalladium(O) catalyst. The catalyst on the solid support perform C-C bond formation reactions such as Heck, Suzuki, Sonagashira, and Stille type reactions of haloarenes that include unreactive chloroarenes. Layered double hydroxides and Merrifield resin supported nanopalladium catalysts are prepared by an exchange of PdC142- followed by reduction and well characterized for the first time. This invention particularly relates to an eco-friendly process employing re-usable heterogeneous catalyst in place of soluble palladium catalysts for preparing coupling products by C-C bond formation reaction of haloarenes that include unreactive chloroarenes in the presence of base. The ligand free heterogeneous layered double hydroxides supported nanopalladium (LDH-Pd°) catalyst using the basic LDH in place of basic ligands indeed exhibits higher activity and selectivity in the C-C coupling reactions of haloarenes that include electron poor and electron rich chloroarenes in nonaqueous ionic liquids (NAIL) over the homogeneous PdC12 system. The coupling products find good applications as intermediates in the preparation of materials, natural products, and bioactive compounds. There are serious disadvantages in performing the catalytic C-C bond formation reaction with iodoarenes and bromoarenes in the manufacture of olefins due to high cost of the starting materials. Despite the synthetic elegance and high turnover number, these coupling reactions suffer from serious limitations of using the expensive bromo and iodoarenes that precluded the wide use in industry. By employing the heterogeneous catalytic system and chloroarenes as starting materials, the cost naturally comes down due to easy recovery of the catalyst and low cost of chloroarenes when compared with bromo and iodoarenes. References may be made to the publications, Organometallics 1992, 11, 1995, Angew. Chem. Int. Ed. 1998,37,481, J. Organomet. Chem.1998, 572, 93, Angew. Chem. Int. Ed. Engl. 1995, 34, 2371, J. Organomet. Chem. 1999, 576, 23 wherein Heckolefination of chloroarenes is carried by palladium complexes under homogeneous conditions. The inherent disadvantages are difficulty in the recovery of palladium and usage of activated electron poor and nonactivated electron neutral chloroarenes. References may be made to the publications Organometallics 1993, 12, 4734, J. Org. Chem. 1999, 64, 10, .7. Am. Chem. Soc. 2001, 723,6989, Synlett, 2000, //, 1589, J. Am. Chem. Soc. 1999, 727, 2123 wherein olefins are prepared from deactivated highly electron rich chloroarenes by palladium complexes. The inherent disadvantage is the usage of expensive sterically hindered phosphine palladium complexes. Reference may be made to the publication Chem. Eur. J. 2000, 6, 1017 wherein Heck-olefination of deactivated highly electron rich chloroarenes is carried by palladacycle catalysts in the presence of nonaqueous liquids. The inherent disadvantages are the usage of additives and low yields. Reference may be made to European patent DE-A 197 12 388.0,1997 wherein Heck-olefination of chloroarenes is carried by palladacycle catalyst using an additive. The inherent disadvantage is that no reaction occurs in the absence of phosphonium salt. Reference may be made to the publications J. Am. Chem. Soc., 1998, 120, 9722 and Angew. Chem. Int. Ed, Engl., 1998, 37, 3387 wherein biphenyls are prepared using arylchlorides with palladium catalysts. The inherent disadvantage is the usage of expensive, air-sensitive phosphine ligands. Reference may be made to a publication J. Organometallic Chem., 1998, 557, 93 wherein biphenyls are prepared using carbene ancillary ligands with aryl bromides and activated aryl chlorides with palladium catalyst. The drawbacks are longer reaction times and yield from the aryl chloride was relatively low. Reference may be made to a publication J. Organomet. Chem. 2001, 634, 39 wherein diarylacetylenes are prepared using heterogeneous polymer anchored bis(pyrimidine)-based palladium catalyst with chlorobenzene with impressive turnover frequency. The drawback is that it was not tried for electron rich chloroarenes. Reference may be made to the publication Synlett, 2000, 1043 wherein arylstannanes were prepared using palladium catalyst in the presence of potassium acetate. The drawback is that the usage of aryl iodides as substrates. Objects of the inventio* The main object of the present invention is to provide novel ligand free reusable heterogeneous nanopalladium(O) catalysts on solid support selected from LDH and S'- NRaX wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl , X is selected from the group consisting of Cl, Br, I, F, OH and OAc. Yet another object is to provide a process for the preparation of novel ligand free reusable heterogeneous nanopalladium (0) catalysts on solid support selected from LDH and S'-NR3X wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl and butyl, X is selected from the group consisting of Cl, Br, I, F, OH and OAc. Yet another object is to provide a process to proform C-C bond coupling reactions such as Heck, Suzuki, Sonagashira, and Stille type reactions with haloarenes by using the said novel ligand free reusable heterogeneous nanopalladium (0) catalyst. Yet another object of the present invention is to reduce the C-C coupling reaction time by employing microwave irradiation. By using microwave irradiation, the rate of C-C coupling reaction is accelerated manifold with the highest turnover frequency ever recorded both in the case of electron poor and electron rich chloroarenes. Still another object of the present invention is to recover the heterogeneous palladium catalyst used in the C-C coupling reactions such as Heck, Suzuki, Sonagashira, and Stille type reactions by simple filtration and reuse for number of cycles with consistent activity. The novelty of the present invention lies in the preparation of Layered double hydroxides and Merrifield resin supported nanopalladium catalysts by an exchange of PdCl4 2" with support selected from Layered double hydroxides and Merrifield followed by reduction and its characterization.Accordingly, the present invention provides, a process for the preparation of a reusable heterogeneous nanopalladium(o) catalyst comprising characterized in that exchanging PdC142- " by reacting sodium palladate of formula Na2PdC142- " with a solid support selected from Layered double hydroxide(LDH) and S'-NR3X wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl , X is selected from the group consisting of C1, Br, I, F, OH and OAc in an aqueous solvent at temperature ranging between 20 to 30 °C for a period ranging from 5 to 24 h under nitrogen atmosphere, reduction by a reducing agent hydrazine hydrate, filtration and washing to obtain the desired catalyst containing the palladium content in the range between 0.1 to 3 mol% with respect to the substrate. The present process further states reacting sodium palladate of formula Na2PdCl42- " with a solid support LDH of formula (M(II)1-xM(III)x (OH)2x+ ) and anionic An-zH2O layers, wherein Mn is a divalent cation selected from the group consisting of Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Ca2+ and M111 is a trivalent ion selected from the group consisting of Al3+, Cr3+, Mn3+, Fe3+ and Co3+, An- is an interstitial anion selected from nitrate, carbonate and chloride, x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4 in an aqueous solvent at temperature ranging between 20 to 30 °C for a period ranging from 5 to 24 h under nitrogen atmosphere followed by reduction, filtration and washing to obtain the desired catalyst. The present invention further states reaction of sodium palladate of formula Na2PdC142- with a solid support S'-NR3X wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl , X is selected from the group consisting of CI, Br, I, F, OH and OAc in an aqueous solvent at a temperature ranging between 20 to 30 °C for a period of 5 to 24 h under the nitrogen atmosphere followed by reduction, filtration and washing to obtain the desired catalyst. The present invention further comprising reacting sodium palladate of formula NajPdCU with a solid support S'-NRjX wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl and butyl, X is selected from the group consisting of Cl, Br, I, F, OH and OAc in an aqueous solvent at a temperature in the range of 20 to 30° C for a period of 5 to 24 h under nitrogen atmosphere followed by reduction, filtration and washing to obtain the desired catalyst. In an embodiment of the present invention the reducing agent used for reduction of solid palladium catalyst is hydrazine hydrate. hi yet another embodiment the organic solvent used in reduction is ethanol. hi yet another embodiment the palladium content in the heterogeneous nanopalladium(O) catalyst obtained is in the range of 0.1 to 3 mol% with respect to the substrate. In yet another embodiment the nanopalladium (0) catalyst obtained is recovered by simple filtration. In still another embodiment the nanopalladium (0) catalysts obtained is reusable for several cycles with consistent activity. Heterogeneous nanopalladium(O) catalysts are prepared by an exchange of PdCU2" on the support selected from LDH and S'-NRsX wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl, X is selected from the group consisting of Cl, Br, I, F, OH and OAc in an aqueous solvent at a temperature ranging between 20 to 30 °C for a period ranging from 5 to 24 h under nitrogen atmosphere followed by filtration and reduction with hydrazine hydrate in ethanol at room temperature . Filtration gave the desired nanopalladium(O) catalysts. C-C bond coupling products are prepared by using the recyclable nanopalladium(0) catalysts by Heck, Suzuki, Sonagashira, and Stille type reactions of haloarenes that include unreactive chloroarenes in a under standard thermal and microwave conditions using solvents selected from nonaqueous ionic liquid , water, THF, dioxan, and NMP at a temperature ranging between 20 to 150 °C for a period 0.5 to 48 h under nitrogen atmosphere, and obtaining the pure C-C coupling products by a conventional method. The palladium content in the catalyst ranges between 0.1 to 3 mol% with respect to the substrate. Nanopalladium (0) catalysts are recovered by simple filtration and reused for several cycles with consistent activity. The solvents selected for the C-C bond formation reaction is selected from the group consisting of nonaqueous ionic liquid, water, 1,4-dioxane, THF, NMP or any mixture thereof. The base used is selected from the group consisting of triethylamine, tributylamine, potassium fluoride, potassium acetate. In the present invention, we synthesized LDH, silica, resin supported nanopalladium catalysts for the first time and used in catalytic amounts for preparing coupling products by C-C bond formation reactions involving Heck-, Suzuki-, Sonogashira- and Stille type coupling of haloarenes that include chloroarenes in presence of base. Heterogeneous nano^alladium(O) catalysts are prepared by an exchange of PdCU2" followed by reduction on silica or resin or LDH . The nanopalladium (0) on supports is responsible for the activity of catalyst in C-C coupling reactions. The activity of heterogeneous nanopalladium catalysts is similar or higher than the homogeneous counter parts. The basic support, Mg-Al layered double hydroxides (LDH) is selected as the material of choice, which not only stabilizes the nanopalladium particles but also provides the adequate electron density to the anchored Pd° species to facilitate oxidative addition of even the deactivated electron rich chloroarenes. Higher yields and stereoselectivities are obtained when nanopalladium catalysts are used. Incidentally this forms the first report of heterogeneous palladium catalyst employed in the Stille type coupling. The consistent activity obtained for several cycles makes the process economical and possible for commercial realization. The coupling products find good applications as intermediates in the preparation of materials, natural products, and bioactive compounds. Thus this invention offers the best techno-economic route for the synthesis of coupling products. Therefore, nanopalladium catalysts are better option for the C-C bond formation reaction of haloarenes that include chloroarenes. Nanopalladium catalysts are prepared as exemplified and used in catalytic amounts for preparing coupling products by C-C bond formation reaction in presence of base in a heterogeneous way as described in the examples. The following examples? are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the invention. Preparation of Nanopalladium catalysts Example 1 Preparation of LDH (Mg-Al-Cl) (1) A mixture of MgCl2.6H2O (30.49 g, 0.15 mmol) and A1C13.6H2O (12.07 g, 0.05 mmol) was dissolved in 200 ml of deionised water. To this aqueous solution, 100 ml of NaOH (2M) solution was slowly added at 25°C and a further amount of 2M NaOH solution was added to maintain a pH of 10 under nitrogen flow. The resulting suspension was stirred overnight at 70°C. The solid product was isolated by filtration, washed thoroughly with deionised water and dried overnight at 80°C. All the synthetic steps were carried out using decarbonated water. Example 2 Preparation of Na2PdCl4 (2) Na2PdCU was prepared by refluxing PdCl2 (1.77 g, 10 mmol) and sodium chloride (0.58 g, 10 mmol) in 50 mL for 4 h. The solution was filtered in hot condition to avoid NaCl contamination. Evaporation of the filtrate gave dark brown flakes (2.88 g, Example 3 Preparation of LDH-PdCL, (3) Mg-Al-Cl (1.5 g) was suspended in 150 mL of aqueous Na2PdCl4 (0.441 g, 1.5 mmol) solution and stirred at 25°C for 12 h under nitrogen atmosphere. The solid catalyst was filtered, washed thoroughly with 500 mL of water and vacuum-dried to obtain 1.752 g of LDH-PdCU (0.86 mmol of Pd per gram). Example 4 Preparation of LDH-Pd° (4) LDH-PdCU (1 g) was reduced with hydrazine hydrate (1 g, 20 mmol) in ethanol (10 mL) for 3 h at room temperature, filtered and washed with ethanol to give an air stable black powder (0.95 mmol of Pd per gram). Example 5 Preparation of Resin-PdCU (5) Resin was obtained by quaternization of triethylamine (2.1 mL, 21 mmol) with one gram of chloromethylated styrene-divinylbenzene copolyrner (Merrifield resin, capacity -2.1 mequiv/g) in chloroform (20 mL) under reflux for 24 h. Quaternary ammonium resin (1 g) was suspended in 100 mL of (0.294 g, 1 mmol) aqueous NaiPdCU solution and stirred at 25°C for 12 h under nitrogen atmosphere. The solid catalyst was filtered, washed thoroughly with water (300 mL) and vacuum-dried to obtain resin-PdCU (0.8 mmol of Pd per gram). Example 6 Preparation of Resin-Pd0 (6) Resin-PdCU (1 g) was reduced with hydrazine hydrate (1 g, 20 mmol) in ethanol (10 mL) for 3 h at room temperature, filtered and washed with ethanol to give an air stable black beads (0.87 mmol of Pd per gram). Example 7 Preparation of Silica-PdCL, (7) Modified silica was obtained by quaternization of triethylamine (0.7 mL, 7 mmol) with bromopropylsilica (capacity 0.7 mequiv/g) in chloroform (20 mL) under reflux for 24 h. 1 g of quaternary ammonium silica was suspended in 100 mL of 0.33 mmol aqueous NaaPdCU solution and stirred at 25°C for 12 h under nitrogen atmosphere. The solid catalyst was filtered, washed thoroughly with 300 mL of water and vacuum dried to obtain SiO2- PdCl4. Example 8 Preparation of Silica-Pd0 (8) Silica-PdCU (1 g) was reduced with hydrazine hydrate (1 g, 20 mmol) in ethanol (10 mL) for 3 h at room temperature, filtered and washed with ethanol to give an air stable black powder. C-C Bond forming reactions The C-C bond forming reactions were performed using LDH-Pd° catalysts to evaluate nanopalladium catalysts of the present invention. 1. Heck-Olefmation. , [NBu4]Br thermal/microwave R = H, OCH3, NO2, CH3, etc. R' = aryl, vinyl Yield = 80 - 95% (microwave) 76 - 98% (thermal) Time=0.5-lh (microwave) 10- 40 h (thermal) Scheme 1 Example 9 Heck-Olefination between chlorobenzene and styrene catalysed by LDH-Pd° under thermal conditions In a 100 mL Schlenk flask, the NAIL (3.23 g, 10 mmol) was heated to melt (130°C) and degassed with nitrogen and vacuum prior to the addition of other reagents. After cooling the NAIL to room temperature, LDH-Pd° (3 mol%), tri-n-butyl amine (222mg, 1.2 mmol) were added. The styrene (1.2 mmol) and chlorobenzene (1 mmol) were then added and the reaction was heated to 130°C and stirred for 10-40 h under nitrogen atmosphere. After completion of the reaction, the LDH-Pd° catalyst was filtered and washed with water and dichloromethane. After removing the solvent, the crude material was chromatographed on silica gel or recrystallized from ethanol to afford the /ra/w-stilbene. Examples 10-17 The procedure was followed as in example 9 with various substrates under thermal conditions and the results are presented in Table 1. Table 1. LDH-Pd° Catalyzed Heck-Olefmation of Chloroarenes under thermal conditions0 Example Chloroarene Olefin Time (h) Yield (%) (Figure Removed) "Chloroarene (1 mmol), olefin (1.2 mmol) LDH-Pd°(3 mol%), [NBu4]Br (10 mmol), and tri-w-butyl amine (1.2 mmol). Reactions are conducted at 130°C. * The values in parentheses refer to the homogeneous reaction conducted with PdCl2 under identical conditions. Example 18 Heck-Olefmation between chlorobenzene and styrene catalysed by LDH-Pd° under microwave conditions. Styrene (1.2 mmol), chlorobenzene (1 mmol), LDH-Pd° (3 mol%), tri-n-butyl amine (222mg, 1.2 mmol) and NAIL (3.23 g, 10 mmol) were taken in a teflon vessel, closed and irradiated in a Miele Electronic M270 microwave oven at 400W and 130°C for 0.5-1 h. After completion of the reaction, the LDH-Pd° catalyst was filtered and washed with water and dichloromethane. After removing the solvent, the crude material was chromatographed on silica gel to afford the /rans-stilbene. Examples 19-26 The procedure was followed as in example 18 with various substrates under microwave conditions and the results are presented in Table 2. Table 2. LDH-Pd Catalyzed Heck-Olefination of Chloroarenes under microwave conditions0 Example Chloroarene Olefin Time (h) Yield (%) (Figure Removed) Chloroarene (1 mmol), olefin (1.2 mmol) LDH-Pd° (3 mol%), [NBu4JBr (10 mmol), and tri-/j-butyl amine (1.2 mmol). Microwave power 400W and temperature 130°C. Examples 27-32 In an effort to compare the reactivity of LDH-Pd° with other heterogeneous catalysts namely Pd/C, Pd/SiOi, resin-Pd0 and Pd/AhOs in the Heck-olefination, separate experiments were conducted under identical conditions with the same ingredients and the results are summarized in Table 3. The activity of various catalysts in the Heckolefination of 4-chloroanisole is found to be in the order: LDH-Pd°>resin- Pd°>Pd/C>Pd/Al2O3>Pd/SiO2. These results indicate that the basic support, LDH facilitates the oxidative addition of Pd° with 4-chloroanisole and eventually the Heckolefination reaction. The procedure was followed as in example 9 with various catalysts between 4- chloroanisole and styrene under thennal conditions and the results are presented in Table 3. Table 3. Heck-Olefination of 4-Chloroanisole with Styrene Using Various Palladium Catalysts0 " 4-chloroanisole (1 mmol), olefm (1.2 mmol), Palladium catalyst (3 mol%), (Table Removed) [NBmJBr 3.23 g (10 mmol), and tributylamine (1.2 mmol) were stirred at 130°C for 40 h. 2. Suzuki coupling Scheme 2 B(OH)2 LDH-PdO base, ioo°C Example 33 Suzuki coupling between chlorobenzene and phenylboronic acid catalysed by LDHPd° Chlorobenzene (1 mmol), phenylboronic acid (1.5 mmol), potassium fluoride (3 mmol), LDH-Pd° (1 mol%) and 1,4-dioxane-water (5:1,5 mL) were charged in a roundbottomed flask. Reactions were carried out at 100°C for 10 h. After completion of the reaction (monitored by TLC), the catalyst was filtered and the reaction mixture was poured into water and the aqueous phase was extracted with ether. After drying, the corresponding product was purified by crystallization from diethyl ether-pentane. Examples 34-40 The procedure was followed as in example 33 and the results are given in Table 4. Table 4. Suzuki Coupling Reactions of Chloroarenes with Arylboronic Acids" Example Arylboronic acid Haloarene Yield(%) " Chloroarene (1 mmol), arylboronic acid (1.5 mmol), LDH-Pd° (1 mol%) and KF (3 mmol), 100°C, 10 h. All the reactions were carried out with 1,4-dioxanewater (5:1, 5 mL) as solvent. * Under NAIL conditions, 8 h. 3. Sonogashira Coupling LDH-Pd°(1 mol%) base, 80°C Example 41 Sonogashira coupling between chlorobenzene and phenylacetylene catalysed by LDH-Pd° To a stirred slurry of chlorobenzene (1 mmol), cuprous iodide (7.6mg, 0.04 mmol), and LDH-Pd° (1 mol%), in THF (2 mL) and water (4 mL) was added triethylamine (152 mg, 1.5 mmol). A solution of 1.25 mmol of phenylacetylene in THF (2 mL) was then added over 2 h. After completion of the reaction, the solvent was evaporated, and the residue was treated with pentane. The solution was filtered to obtain the catalyst and evaporation of the solvent gives the coupling product. Examples 42-43 The procedure was followed as in example 41 and the results are given in Table 5. Table S. Cross Coupling Reactions Between Phenylacetylene and Chloroarenes0 Example Chloroarene Phenylacetylene Time(h) Yields (%) 419' = 30 95 27 95* 42 48 60 43 40 82 " Chloroarene (1 mmol), phenylacetylene (1.1 mmol), LDH-Pd° (1 mol%), Et3N (1.5 mol), 80°C. All reactions were carried out with THF-water (1:1,8 mL) as solvent system. * Under NAIL conditions. 4. Stille type coupling Cl base, so°c Scheme 4 Example 44 Stille type couping between chlorobenzene and tributyltin reagent catalysed by LDH-Pd° A round-bottomed flask was charged with LDH-Pd° (1 mol%), potassium acetate (294mg, 3 mmol), and NMP (4 ml). To this 4-chloroanisole (1 mmol) and tributyltin hydride (2 mmol) were added successively, and the mixture was stirred at 50° C for 16 h. The reaction mixture was diluted with benzene, washed with water and catalyst was collected for next cycle. Examples 45-49 The procedure was followed as in example 44 and the results are given in Table 6. Table 6. Stannylation of Haloarenes with LDH-Pd° catalyst0 Example Chloroarene Tin reagent Yield Bu3Sn-H Bu3Sn— H Bu3Sn— ,. " Chloroarene (1 mrnol), trialkyltin reagent (2 mmol), potassium acetate (3mmol), LDH-Pd° (2 mol%). All the reactions were carried out with NMP as solvent, 50°C, 16 h. * Under NAIL conditions, 12 h. The main advantages of the present invention are: 1. A novel and ecofriendly process for the synthesis of coupling products from haloarenes that include highly unreactive chloroarenes by C-C bond formation is presented. 2. The present process dispenses the use of soluble palladium catalysts instead a heterogeneous reusable LDH-Pd(O) is used. 3. Nanopalladium catalyst, LDH-Pd(O) is prepared and used as heterogeneous catalyst for the synthesis of coupling products by C-C bond formation reactions. The use of heterogeneous nanopalladium catalyst precludes the presence of palladium in traces with the product. 4. The stereoselectivity and the yields are good. 5. The work-up procedure is simple. 6. The catalyst is subjected to many recycles, which displayed consistent activity. 7. The present process is environmentally safe since there is no disposal problem. 8. The process is economical. We claim: 1. A process for the preparation of a reusable heterogeneous nanopalladium(o) catalyst comprising characterized in that exchanging PdC142- by reacting sodium palladate of formula Na2PdC142- with a solid support selected from Layered double hydroxide(LDH) and S'-NR3X wherein S' is a unmodified surface support selected from resin and silica, R is an alkyl group selected from the group consisting of methyl, ethyl, propyl, butyl , X is selected from the group consisting of C1, Br, I, F, OH and OAc in an aqueous solvent at temperature ranging between 20 to 30 °C for a period ranging from 5 to 24 h under nitrogen atmosphere, reduction by a reducing agent hydrazine hydrate, filtration and washing to obtain the desired catalyst containing the palladium content in the range between 0.1 to 3 mol% with respect to the substrate. 2. A process as claimed in claim 1, wherein a solid support LDH is of formula (M(II)1-xM(III)x (OH)2x+ ) and anionic An- ~zH2O layers, wherein M11 is a divalent cation selected from the group consisting of Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Ca2+ and Mm is a trivalent ion selected from the group consisting of Al3+, Cr3+, Mn3+, Fe3+ and Co3+, An- is an interstitial anion selected from nitrate, carbonate and chloride, x is the mole fraction having integral value ranging from 0.2 to 0.33, and z is the number of water molecules and ranges from 1 to 4. 3. A process as claimed in claims 1-2, wherein the aqueous solvent is selected from water or ethanol. 4. A process for the preparation of reusable nanopalladium (o) catalyst substantially as herein described with reference to the examples.

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