Title of Invention

A PROCESS FOR THE PREPARATION OF AN IMPROVED RHODIUM CATALYST

Abstract

A process for the preparation of an improved rhodium catalyst which comprises reacting rhodium compound with an alkali metal salt of the substituted chiral phenylacetic acid in the presence of an organic solvent such as aliphatic alcohols at a temperature in the range of 80°C to 100°C, for a period ranging between 6-8 hrs., cooling the reaction mixture to room temperature, removing the solvent by conventional methods and isolating the catalyst by standard methods.

Full Text

This invention relates to a process for the preparation of an improved rhodium catalyst. More particularly, this invention relates to the preparation of the said chiral, water-soluble, phosphorous free catalyst having the structural formula Rh2[(C6H5)C(CF3)(OCH3)(CO2)]4 from anhydrous rhodium chloride RhCl3 and alkali metal salt of α-methoxy-α-trifluoromethylphenyl acetic acid [(C6H5)C(CF3)(OCH3)(CO2H)]. Rhodium complexes are chiefly used as catalysts in organic reactions and in industry, there are quite a few practical applications of rhodium complexes. Rhodium (11) carboxylates are used in chemotherapy and though they are less effective than Platinum (II) complexes, unwelcome side effects are fewer with Rh (II) carboxylates. Additionally, rhodium complexes are reported to have been used as radiation sensitisers. In the prior art, it has been shown that a catalyst derived from rhodium chloride has been efficiently utilised for the oligomerisation of terminal alkynes under homogeneous and biphasic conditions [Baidossi, Wael., et.al. J.Mol.Catal., 85 (2), 153-62, 1993]. Also water-soluble chira! aza-phosphaadamantane complexes as ligands witr rhodium chloride trihydrate for the hydrogenation of aldehydes and olefins have been reported [Darensbourg, Donald.J., Organometallics, 11(6). 1990-1993, 1992.] Most of the above mentioned methods suffer from the following drawbacks. I. Most or all the catalysts possess phosphorous ligands in the form of organo phosphorous compounds, sometimes sulphonated to enable better solubility. These ligands are efficient at ambient temperature and pressure. 2. At higher temperatures and pressures, the catalysts do not perform efficiently, as they tend to dissociate or get converted to other unstable materials. 3. Organophosphorous based ligands in the catalysts are air sensitive, moisture sensitive etc., and tend to degrade to triphenylphosphine oxide which is difficult to get rid off It is therefore desirable to provide a process for the preparation of an improved rhodium catalyst, which is free from phosphorous, having hydrophilic nature etc. The object of the present invention is to provide a process for the preparation of an improved rhodium catalyst, which is water-soluble and free from phosphoro.s ligands Accordingly, the present invention provides a process for the preparation of the improved rhodium catalyst which comprises reacting a rhodium compound with an alkali metal salt of optically active substituted phenyl acetic acid in the presence of an organic solvent such as aliphatic alcohol at a temperature in the range of 80 °C to 100 °C, for a period ranging between 6-8 hrs., cooling the reaction mixture to room temperature, removing the solvent by conventional methods and isolating the catalyst by standard methods. In one of the embodiments of the present invention, the rhodium source used may be anhydrous rhodium chloride or rhodium chloride trihydrate. preferably anhydrous rhodium chloride. In another embodiment the alkali metal salt used may be derived from optically active a-methoxy-α-trifluoromethylphenyl acetic acid (Mosher acid) (R) or (S) form preferably alkali metal salt of R isomer. In another embodiment the alkali metal salt used may be sodium or potassium salt of optically active a-methoxy-a-trifluoromethylphenyl acetic acid (Mosher acid) R form preferably sodium salt of R isomer. In yet another embodiment the solvent used in the reaction may be selected from alcohols like methanol, ethanol or isopropanol etc. preferably ethanol. The process of the present invention is further described herein below with reference to examples which are illustrative only and should not be construed to as limit of the scope of the present invention in any manner. Example 1 These examples illustrate a method for the preparation of the catalyst The sodium salt of substituted chiral phenylacetic acid was prepared by reacting a solution containing sodium hydride (23 mg, 50 % immersion in mineral oil, 0.478 mmol) in anhydrous tetrahydrofuran (5 ml) with R a-methoxy- a-trifluoromethyl phenyl acetic acid (112 mg, 0.478 mmol) at 0°C for ½ an hour. The solvent was removed under reduced pressure (450 mm), the alkali metal salt formed was taken in ethanol (6 ml) and anhydrous rhodium chloride (50 mg, 0.239 mmol) was added to it. The resulting mixture was refluxed for 6-8 hrs. the reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure (450 mm). The required catalyst was obtained as a brownish red solid in an isolated yield of > 88 % (119 mg). Example 2 The sodium salt of substituted chiral phenylacetic acid was prepared by reacting a solution containing sodium hydride (23 mg, 50 % immersion in mineral oil, 0.478 mmol) in anhydrous tetrahydrofuran (5 ml) with R a-methoxy- a-trifluoromethyl phenyl acetic acid (112 mg, 0.478 mmol) at 0 °C for '/S an hour. The solvent was removed under reduced pressure (450 mm), the alkali metal salt formed was taken in ethanol (6 ml) and rhodium chloride trihydrate (63 mg. 0.239 mmol) was added to it. The resulting mixture was refluxed for 6-8 hrs, die reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure (450 mm). The required catalyst was obtained as a brownish red solid in an isolated yield of >79 % (108 mg). Example 3 The sodium salt of substituted chiral phenylacetic acid was prepared by reacting a solution containing sodium hydride (23 mg, 50 % immersion in mineral oil, 0.478 mmol) in anhydrous tetrahydrofuran (5 ml) with R a-methoxy- a-trifluoromethyl phenyl acetic acid (112 mg, 0.478 mmol) at 0 °C for ½ an hour. The solvent was removed under reduced pressure (450 mm), the alkali metal salt formed was taken in methanol (6 ml) and anljydrous rhodium chloride (50 mg, 0.239 mmol) was added to it. The resulting mixture was refluxed for 6-8 hrs. the reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure (450 mm). The required catalyst was obtained as a brownish red solid in an isolated yield of > 55 % (75 mg). Example 4 The sodium salt of substituted chiral phenylacetic acid was prepared by reacting a solution containing sodium hydride (23 mg. 50 % immersion in mineral oil, 0.478 mmol) in anhydrous tetrahydrofuran (5 ml) with R a-methoxy- α-trifluoromethyl phenyl acetic acid (112 mg, 0.478 mmol) at 0 °C for 14 an hour. The solvent was removed under reduced pressure (450 mm), the alkali metal salt formed was taken in isopropanol (6 ml) and anhydrous rhodium chloride (50 mg, 0.239 mmol) was added to it. The resulting mixture was refluxed for 6-8 hrs, the reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure (450 mm). The required catalyst was obtained as a brownish red solid in an isolated yield of > 79 % (108 mg). Example 5 The potassium salt of substituted chiral phenylacetic acid was prepared by reacting a solution containing potassium hydride (27 mg, 35 % immersion in mineral oil, 0.478 mmol) in anhydrous tetrahydrofuran (5 ml) with R a-methoxy- a- trifluoromethyl phenyl acetic acid (112 mg, 0.478 mmol) at 0 °C for ½ an hour. The solvent was removed under reduced pressure (450 mm), the alkali metal salt formed was taken in ethanol (6 ml) and anhydrous rhodium chloride (50 mg, 0.239 mmol) was added to it. The resulting mixture was refluxed for 6-8 hrs, the reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure (450 mm). The required catalyst was obtained as a brownish red solid in an isolated yield of > 85 % (116 mg). We claim !. A process for the preparation of an improved rhodium catalyst which comprises reacting rhodium compound with an alkali metal salt of the substituted chiral phenylacetic acid in the presence of an organic solvent such as aliphatic alcohols at a temperature in the range of 80°C to 100°C for a period ranging between 6-8 hrs., cooling the reaction mixture to room temperature, removing the solvent by conventional methods and isolating the catalyst by standard methods. 2. A process as claimed in 1 wherein the rhodium source used may be anhydrous rhodium chloride or rhodium chloride trihydrate, preferably anhydrous rhodium chloride. 3. A process as claimed in claims 1 and 2 wherein the alkali metal salt used may be derived from optically active a-methoxy-α-trifluoromethylphenyl acetic acid (Mosher acid) (R) or (S) form preferably alkali metal salt of R isomer. 4. A process as claimed in claims 1-3 wherein the alkali metal salt used may be sodiun; or potassium salt of optically active α-methoxy-α-trifluoromethylphenyl acetic acid (Mosher acid) R form preferably sodium salt of R isomer. A process as claimed in claims 1-4 wherein the solvent used in the reaction may be selected from alcohols like methanol, ethanol or isopropano! preferably ethanol A process for the preparation of an improved rhodium catalyst as fully-described herein before with reference to examples.

Documents:

1398-del-1999-abstract.pdf

1398-del-1999-claims.pdf

1398-del-1999-complete specification (granded).pdf

1398-del-1999-correspondence-others.pdf

1398-del-1999-correspondence-po.pdf

1398-del-1999-description (complete).pdf

1398-del-1999-form-1.pdf

1398-del-1999-form-19.pdf

1398-del-1999-form-2.pdf