GB1580461A - Transition metal complexes - Google Patents

Abstract

For the asymmetrical hydrogenation of substrates selected from prochiral olefins and compounds containing CO and/or CN groups, the olefin of interest here is contacted with a complex of a transition metal with an asymmetrical aminophosphine. The asymmetrical aminophosphine is selected from those of the formula PR@(NR<2>R<3>)3-x where R<1>, R<2> and R<3> are as defined in the claims. The catalytic system as a means for carrying out the abovementioned asymmetrical hydrogenation contains a complex obtained by a reaction starting from compounds of the formula (R<3>R<2>N)nX and a coordination compound of a metal from the transition series.

Description

(54) TRANSITION METAL COMPLEXES (71) We, SNAMPROGETTI S.P.A., an Italian Company, of Corso Venezia 16, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to transition metal complexes and to their use as catalysts in the asymmetrical hydrogenation of prochiral and racemic ethylenically unsaturated compounds and of compounds containing CO and/or CN groups.

The preparation on an industrial scale of optically active organic compounds having high optical purity, for instance levorotatory amino acids, is almost exclusively carried out by processes of the biochemical or microbiological type.

Until recently, there were known no purely chemical processes which were able to complete with the biochemical or microbiological processes in terms of economy and optical yield. However, the discovery of new homogeneous catalytic systems having a high stereospecificity, for example tris(triphenyl-phosphine)chlororhodium, and new developments in the synthesis of phosphines containing asymmetrical phosphorus, lead.to the preparation of transition metal chiral complexes having a high stereo-selectivity in the hydrogenation of prochiral olefins.

According to the present invention, there is provided a complex of (a) a coordination compound of a transition metal and (b) an optically-active aminophosphine containing at least one chiral centre.

The aminophosphine preferably has the general formula: PRx'(NW'R"')3, wherein R' is a monovalent organic radical, x is 0, 1 or 2, and R" and R"' are the same or different and each is a monovalent organic radical at least one of which contains one or more chiral centres. Preferably, R' of the aminophosphine is an alkyl group, an aryl group, an alkylaryl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylphosphino group (as herein defined), an arylphosphino group (as herein defined) or an aminophosphino group (as herein defined), and R" and R"' of the aminophosphine are the same or different and each is an alkyl group, an aryl group, an alkylaryl group or a cycloalkyl group at least one of which contains one or more chiral centres.

The terms (1) "alkylphosphino", (2) "arylphosphino" and (3) aminophosphino" used herein mean respectively:

(1) alkyl alkyl P- or P-alkylene alkyl alkyl (2) aryl aryl P- or P-arylene aryl aryl (3) NH NHy K P- or P-NH NH2 NH2 The invention also provides a process for the preparation of a transition metal complex of the invention, which comprises reacting an optically-active aminophosphine containing at least one chiral centre with a coordination compound of a transition metal.

The invention further provides a process for the asymmetrical hydrogenation of a prochiral or racemic ethylenically unsturated compound, which comprises contacting the compound with a complex of the invention.

The invention further provides a process for the asymmetrical hydrogenation of a compound containing a CO and/or CN group, which comprises contacting the compound with a complex of the invention.

The radical NR"R" in the above general formula is an optically active amino group derived from an amino compound. Thus, the radical NR"R" may be selected from a wide category of mono- and poly-dentate ligands capable of coordinating with transition metal compounds to form complexes suitable for asymmetrical hydrogenation of prochiral and racemic olefins to produce the corresponding saturated compounds, and of compounds containing CO and/or CN groups.

The preparation of the aminophosphines can be carried out by reacting an organic amine or alkali metal derivative thereof with a halophosphine, e.g. a chlorophosphine. Thus, for example, the preparation of the aminophosphines can be carried out according to one of the following schemes: (1) R*NH2+ R2PCI + BeR*NHPR2+ HCI (2) RR*NH+R2PCl+BRR*N-PR2+HCl (3) RR*NNa+R2PClRR*NPR2+NaCl (4) 2RR*NH+RPCI2+2B(RR*N)2PR+2B . HCI (5) R*NH2+2R2PCI+2B < R*N(PR2)2+2B . HCI (6) RR*N),PR+ ROH-+(RR*N)PR(OR)+ RR*NH (7) 3RR*NH+PC1,+3B-(RR*N),P+3B . HCI, wherein the groups R have the above meanings and B is an organic base. The preparation can be carried out according to processes already known for the corresponding achiral compounds.

Examples of the optically active amines R*NH2 are a methylbenzylamine, bornylamine, sec.-butylamine, menthylamine or any primary amine containing one or more chiral centres. In the secondary amines R*RNH, one or both of the groups attached to the nitrogen atom can contain one or more chiral centres. Examples of such secondary amines are unsubstituted N-methyl-a-methyl-benzylamine, pipecoline, desoxyephidrine, O-substituted ephedrines, N-monosubstituted and N,N'-disubstituted ethylenediamines with at least one chiral centre and piperazines containing one or more chiral centres.

The active catalytic complex is formed in the asymmetrical hydrogenation by reacting the aminophosphine with a coordination compound of a transition metal, preferably Cr, Mo, W, Fe, Co, Ni, Ru, Rh, Pd, Pt, Os, Ir, Cu, Ag, Au, Ti or V.

The ligands of the coordination compounds can be anionic or neutral.

Examples of anionic ligands are halogens, cyanide, nitrate, acetate, acetylacetonate and sulphide. Examples of neutral ligands are water, ammonia, amines, phosphines, carbon monoxide, olefins and diolefins. Examples of coordination compounds are rhodium(lII) hydrated chloride, ruthenium(II) chloride, dichloro-tetrakis(triphenylphosphine)ruthenium(II), rhodium(I) ,u-dichloro-tetrakis(ethylene), rhodium(I) -dichloro-bis(norbornadiene), dichloro-tetraamino-platinum(II) and dibromo-tetrakis(triphenylphosphine)palladium.

The molar ratio between the aminophosphine and the transition metal compound, as expressed as the ratio between the number of phosphorus atoms of the aminophosphine and the number of transition metal atoms, is preferably from 1:1 to 15:1, the ratios 2:1, 3:1 and 4:1 being most preferred.

The reaction solvent, if such is used, is preferably an aromatic hydrocarbon, an aliphatic hydrocarbon, an alcohol, an ether, a ketone, an ester, an amide or a mixture of two or more thereof.

The asymmetrical hydrogenation is preferably carried out at a molar ratio of substrate to catalyst of from 10,000:1 to 10:1. The reaction temperature is preferably from -70 to 2000 C., more preferably from 0 to 500 C. The hydrogen pressure is preferably in the range of 1 to 100 atmospheres.

The following Examples illustrate the invention.

EXAMPLE 1 N,N'-bis(S(-)a-methylbenzyl)ethylenediamine was prepared from S(-)amethylbenzylamine and diethyl oxalate. The diamide was reduced with lithium aluminium hydride in tetrahydrofuran (THF) and the corresponding diamine was isolated as its dihydrochloride. The latter had a melting point of 250"C and was obtained in a yield of 80%.

The dihydrochloride was treated with 10% NaOH, and 0.050 mols of the diamine thus obtained were treated with 0.100 mols of diphenylchlorophosphine in 300 ml of anhydrous benzene, in the presence of 0.200 mols of triethylamine.

The mixture was refluxed for 20 hours, the triethylammonium hydrochloride formed then being filtered off and the benzene solution being concentrated until N,N'-bis(S(-)a-methylbenzyl)-N,N'-bis(diphenylphosphino)ethylenediamine separated. The yield of product was 70% with respect to the starting diamine, and the product had a melting point of 138--140"C and an optical rotation [a]g of -91.5 (c=l in CHCl3).

A catalyst was prepared by treating 5.5 mg of rhodium(I) ,u- dichlorotetrakis(ethylene) (17.7x 10-6 mols) with 22.5 mg of N,N'-bis(S(-)a- methylbenzyl)-N,N'-bis(diphenylphosphino)ethylenediamine (35.4x 10-6 mols), 6 ml of anhydrous benzene being used as solvent. The atomic ratio P/Rh was 2.

The solution was transferred into a flask containing 2.8 g of - acetylamidocinnamic acid in 24 ml of anhydrous methanol, the flask being connected to a hydrogenating apparatus operating at atmospheric pressure and kept at 250C by a thermostat. A careful purge with hydrogen of the reaction environment was effected before the catalytic complex was added. The reaction was monitored by means of normal monitoring techniques. The initial rate of hydrogen absorption was about 4 ml/minute under the operating conditions.

After 3 hours, the conversion was about 85%. The reaction was terminated and the reaction product was separated by evaporating the solvent under reduced pressure.

The product was treated with a 0.5N NaOH solution, and the insoluble catalyst was filtered off. The aqueous solution was brought to a pH of 2-3 by the addition of dilute HCI, and the organic phase was extracted five times with ethyl ether. The ether extracts were combined and dried over Na2SO4. The ether was then evaporated. The product, according to its NMR and IR spectrographs, consisted of R(-)N-acetylphenylalanine. Its optical rotation [ce]2D was -40 (c=l in 95 /" EtOH), and the optical yield was 84%. The optical rotation [a]2D0 of enantiomerically pure S(+)N-acetylphenyl alanine is +47.5 (c=l in 95 /" EtOH).

EXAMPLE 2 By repeating the process described in Example 1 using R(+)amethylbenzylamine, N,N' - (R(+)a - methylbenzyl) - N,N' - (diphenyl phosphino)ethylenediamine was prepared, having two centres of chirality of opposite configuration with respect to the diphosphine of Example 1.

The product was reacted with the rhodium compound used in Example 1, and the catalytic complex obtained was used in the hydrogenation of a- acetylaminocinnamic acid. The hydrogenated product was isolated and examined as in Example 1. It consisted of S(+)N-acetylphenylalanine, and had an optical rotation [a]2 of +38.9 (c=l in 95% EtOH) indicating an enantiomeric purity of 82%.

EXAMPLE 3 2(S),5(S)-dimethylpiperazine was prepared by the cyclodimerisation of S(-) alanine and reduction of the resulting diketopiperazine with lithium aluminium hydride.

The subsequent reaction of the above piperazine with diphenylchlorophosphine in the presence of triethylamine lead to the formation of 2(S),5(S)-dimethyl-N,N'-diphenylphosphino (+)-piperazine having an optical rotation [a]2D of +78 (c=l in THF), in a yield of 60%.

By the procedure of Example 1, the thus prepared product (134x10-5 mols) was reacted with rhodium(I) ,u-dichlorotetrakisfethylene) (67x 10-6 mols), and the catalytic complex obtained was used in the hydrogenation of a-acetylamidocinnamic acid (13x 10-3 mols) at 250C under atmospheric pressure. Nacetyl-(S)phenylalanine was thus obtained in a yield of 8O85%. It had an optical rotation [a]20+0.5 (c=l in 95 /n EtOH) and an optical purity of 1%.

EXAMPLE 4 A catalytic complex prepared according to Example 1 from 47.9 mg of rhodium(I) ,u-dichlorotetrakiscyclooctene (66.8x 10-5 mols) and 86 mg of N,N' (S(-)methylbenzyl)-N,N'-(diphenylphosphino)ethylenediamine (135 x 10-6 mols) was used in the catalytic hydrogenation of 3-acetoxy-4-methoxy-a- acetylamidocinnamic acid (2 g) under atmospheric pressure at 250C. By operating as described in Example 1, 3-acetoxy-4-methoxy-N-acetyl-(R)phenylalanine was isolated from the reaction medium in a yield of 85-90%. It had an optical rotation [lr]2D of -16.9 (c=l in acetone). The optical yield was 77%. Enantiometically pure 3acetoxy-4-methoxy-N-acetyl-(R)phenylalanine has an optical rotation [a]2D of -22 (c=l in acetone).

EXAMPLE 5 1-phenyl-2,5-S(-)&alpha;-methylbenzyl-1-phospha-2,5-azacylcopentane was prepared by reacting N,N'-(S(-)&alpha;-methylbenzyl)ethylenediamine with phenyldichlorophosphine in the presence of triethylamine. 380x 10-6 mols of the product were reacted with 95x 10-6 mols of rhodium(I) - dichlorotetrakis(ethylene). The P/Rh ratio was 2.

By the procedure of Example 3 the catalyst was used in the hydrogenation of acetylaminoacrylic acid, under a pressure of 15 atmospheres of hydrogen and at room temperature.

Enantiomerically pure N-acetyl-S(-)alanine was obtained in a yield of 85-90%. It had an optical rotation [a]2 of -5 (c=l in H2O). The optical yield was 7.5.

Enantiomerically pure N-acetyl-R(-)alanine has an optical rotation [cr]2D of 66.5 (c=2 in H9O).

EXAMPLE 6 A catalytic complex prepared according to Example 1 from rhodium(l) y- dichlorotetrakis(ethylene) (73x 10-6 mols) and N,N'-(S(-)cr-methylbenzyl)-N,N'- (diphenylphosphino)ethylenediamine (146x 10-8 mols) was used in the catalytic hydrogenation of 3,4-methylenedioxy-a-acetylamidocinnamic acid (6.98x10-3 mols) at 25 C under atmospheric pressure. By operating as described in Example 1, 3,4-methylenedioxy-N-acetyl(R)phenylalanine was isolated in a quantitative yield.

It had an optical rotation l]'D6 of -40 (c=1.8 in 95% EtOH). The optical yield was 75%.

Enantiomerically pure 3,4-methylenedioxy-N-acetyl-(R)phenylalanine has an optical rotation [CE]18 of -53.4 (c=1.8 in 85% EtOH).

EXAMPLE 7 A catalytic complex prepared according to Example 1 from rhodium(l) y- dichlorotetrakis(cyclooctene) (13.9x10-5 mols) and n,n'-(S(-)a-methylbenzyl)- N,N'-(diphenylphosphino)ethylenediamine (27.5x 10-8 mols) was used in the catalytic hydrogenation at 250C and under atmospheric pressure of aacetylamidoacrylic acid (15.5x 10-3 mols). There was obtained N-acetyl-(R)alanine in a quantitative yield. It had an optical rotation [a]2 of 48.5. The optical yield was 73%.

EXAMPLE 8 A catalytic complex prepared as described in Example I from rhodium (I) ,u-dichlorotetrakis(cyclooctene) (146x 10-8 mols) and n,n'-(S(-)a- methylbenzyl)-n,n'-(diphenylphosphino)ethylenediamine (278x10-5 mols), was used in the catalytic hydrogenation of the methyl ester of a-acetylamidocinnamic acid (13.7x10-3 mols). R(-)N-acetyl-phenylalanine methyl ester was isolated by chromatography on silica gel. It had an optical rotation [s]2D5 Of ~10 (c=l.9 in MeOH). The optical yield was 46.5%.

Enantiomerically pure S(-)N-acetyl-phenylalanine methyl ester has an optical rotation [a]2D of +21.4 (c=1.9 in MeOH).

EXAMPLE 9 A catalytic complex prepared according to Example 1 from rhodium(I) ,u- dichlorotetrakis(ethylene) (77x 10-8 mols) and N,N'-(S(-)a-methylbenzyl)-N,N'- (diphenylphosphino)ethylenediamine (154x10-8 mols), was used in the catalytic hydrogenation of propene-2,3-dicarboxylic acid (15x10-3 mols) at 15.5 atmospheres and 30"C. Propane-2,3-dicarboxylic (R)acid was isolated in a quantitative yield. It had an optical rotation [a]2D of 1.5 (c=l in H2O). The optical yield was 10%.

EXAMPLE 10 A catalytic complex prepared according to Example 1 from rhodium(I) y- dichlorotetrakis(ethylene) (72x 10-6 mols) and N,N'-(S(-)a-methylbenzyl)-N,N'- diphenylphosphino)ethylenediamine (146x10-6 mols), was used in the catalytic hydrogenation of a-methylcinnamic acid at 5 atmospheres and 25"C. 2 Benzylpropionic (S)acid was recovered according to Example I in a quantitative yield. It had an optical rotation []2D of -1 (c=l in benzene). The optical yield was 4% EXAMPLE 11 7 ml of anhydrous methanol and 5 g of acetophenone were charged in an autoclave under nitrogen atmosphere. A solution of 2 ml of benzene containing 18.7 mg of rhodium chloro-norbornadiene dimer, i.e. (RhCINBD)2, and 56.3 mg of N,N' - bis(S(-)a - methylbenzyl) - N,N' - (diphenylphosphino)ethylenediamine, i.e.

PNNP, was then added. After establishing a vacuum in the autoclave, the autoclave was charged with hydrogen to a pressure of 12 atmospheres. After 12 hours at room temperature, 4 atmospheres of hydrogen had been absorbed with a conversion of about 80%. The reaction was stopped at this time. Benzene and methanol were removed under reduced pressure, and, by fractional distillation under vacuum, 3.9 g of a product were then recovered. The NMR spectrograph of the product showed that it consisted of R(+)l-methyl-phenyl-carbinol. It had an optical rotation Ic]20 of +7.4 (pure product). Its optical purity was 17% ([sr]2D=+44.2).

EXAMPLE 12 A catalyst was prepared from 45 mg of(RhClNBD)2 and 124 mg of PNNP in 3 ml of benzene. The catalytic solution was charged into an autoclave containing 5 g of cyclohexylmethylketone in 7 ml of methanol. The autoclave was charged with hydrogen to a pressure of 12 atmospheres. After 48 hours at room temperature, about 3 atmospheres of hydrogen had been absorbed. The reaction was terminated.

In the manner described in Example 1, 3.15 g of a product were recovered. The product was R(-)l-cyclohexylethanol and had an optical rotation [(z]20 of -0.430 (pure compound). The optical yield was 8% ([a]2=-5.5).

EXAMPLE 13 A flask containing 2 ml of benzene was charged with 24.2 mg of (RhCINBD)2 and 66.8 mg of PNNP. Thereafter, 2.28 ml of diphenylsilane were added. The flask was cooled to 0 C, and 1.21 g of acetophenone-anil, i.e. C8H 8-n=C(CH3)-C8H5, in 6 ml of benzene were added dropwise. After 12 hours at OOC, 4 ml of 10% HCI and acetone were added until a homogeneous solution was obtained after filtration of the hydrolysis products. After removal of the acetone under reduced pressure, 100 ml of 5%, HCI were added, and the mixture is extracted six times with 25 ml of diethyl ether, the aqueous phase was made alkaline with 2N NaOH, and an organic phase obtained by extracting four times with 20 ml of diethyl ether was dried over Na2SO4. The ether was then removed. The residue was distilled under vacuum to obtain 700 mg of a compound identified as R(-)N-phenyl-n-methylbenzylamine.

The product had an optical rotation [(r]2,0 of -3.29 (c=2.15 in EtOH). Its optical purity was 12.2 ' ([c]2g=26.1).

EXAMPLE 14 By the procedure described in Example 3 using a catalytic solution of 19 mg of (RhCINBD)2 and 55 mg of PNNP in 2 ml of benzene, 4.3 g of ethyl pyruvate in 10 ml of benzene were reacted with 5.79 of diphenylsilane in 5 ml of benzene. In this Example, contrary to Example 3, the silane was added dropwise to the solution of the other reactants, which solution was kept at OOC. After 2 hours at OOC, hydrolysis was effected by means of 30 ml of MeOH containing 10 mg of ptoluenesulphonic acid. After filtration and removal of the methanol, 3.5 g of D(+)ethyl lactate, having an optical rotation []2g of +3.25, were isolated by fractional distillation. Its optical purity was 22.4% ([a]200-14.5).

WHAT WE CLAIM IS:- 1. A complex of (a) a coordination compound of a transition metal and (b) an optically-active aminophosphine containing at least one chiral centre.

2. A complex according to claim 1, wherein the aminophosphine has the general formula: PRx'(NR"R"')x wherein R' is a monovalent organic radical, x is 0, 1 or 2, and R" and R"' are the same or different and each is a monovalent organic radical at least one or which contains one or more chiral centres.

3. A complex according to claim 2, wherein R' of the aminophosphine is an alkyl group, an aryl group, an alkylaryl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group; an alkylphosphino group (as herein defined), an arylphosphino group (as herein defined) or an aminophosphino group (as herein defined); and R" and R"' of the aminophosphine are the same or different and each is an alkyl group, an aryl group, an alkylaryl group or a cycloalkyl group at least one of which contains one or more chiral centres.

4. A process for the preparation of a transition metal complex as claimed in claim 1, which comprises reacting an optically-active aminophosphine containing at least one chiral centre with a coordination compound of a transition metal.

5. A process according to claim 4, wherein the molar ratio of aminophosphine to transition metal compound is from 1:1 to 15: 1, expressed as the ratio between the phosphorus atoms and transition metal atoms.

6. A process according to claim 4 or 5, wherein the reaction is carried out in a solvent which is an aromatic hydrocarbon, an aliphatic hydrocarbon, an alcohol, an ether, a ketone, an ester, an amide or a mixture of two or more thereof.

7. A process according to claim 4, substantially as described in any one of the foregoing Examples.

8. A transition metal complex whenever prepared by the process claimed in any of claims 4 to 7.

9. A process for the asymmetrical hydrogenation of a prochiral or racemic ethylenically unsaturated compound, which comprises contacting the compound with a complex as claimed in any of claims I to 3 and 8.

10. A process for the asymmetrical hydrogenation of a compound containing a CO and/or CN group, which comprises contacting the compound with a complex as claimed in any of claims 1 to 3 and 8.

11. A process according to claim 9 or 10, wherein the molar ratio of compound to complex is from 10,000:1 to 10:1.

12. A process according to any of claims 9 to 11, wherein the contacting is effected at a temperature of from -70 to 2000 C.

13. A process according to claim 12, wherein the contacting is effected at a temperature of from 0 to 500 C.

14. A process according to any of claims 9 to 13, wherein the contacting is effected under a hydrogen pressure of from 1 to 100 atmospheres.

15. A process according to claim 9, substantially as described in any one of the foregoing Examples I to 10.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. Na2SO4. The ether was then removed. The residue was distilled under vacuum to obtain 700 mg of a compound identified as R(-)N-phenyl-n-methylbenzylamine. The product had an optical rotation [(r]2,0 of -3.29 (c=2.15 in EtOH). Its optical purity was 12.2 ' ([c]2g=26.1). EXAMPLE 14 By the procedure described in Example 3 using a catalytic solution of 19 mg of (RhCINBD)2 and 55 mg of PNNP in 2 ml of benzene, 4.3 g of ethyl pyruvate in 10 ml of benzene were reacted with 5.79 of diphenylsilane in 5 ml of benzene. In this Example, contrary to Example 3, the silane was added dropwise to the solution of the other reactants, which solution was kept at OOC. After 2 hours at OOC, hydrolysis was effected by means of 30 ml of MeOH containing 10 mg of ptoluenesulphonic acid. After filtration and removal of the methanol, 3.5 g of D(+)ethyl lactate, having an optical rotation []2g of +3.25, were isolated by fractional distillation. Its optical purity was 22.4% ([a]200-14.5). WHAT WE CLAIM IS:-

1. A complex of (a) a coordination compound of a transition metal and (b) an optically-active aminophosphine containing at least one chiral centre.

2. A complex according to claim 1, wherein the aminophosphine has the general formula: PRx'(NR"R"')x wherein R' is a monovalent organic radical, x is 0, 1 or 2, and R" and R"' are the same or different and each is a monovalent organic radical at least one or which contains one or more chiral centres.

3. A complex according to claim 2, wherein R' of the aminophosphine is an alkyl group, an aryl group, an alkylaryl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group; an alkylphosphino group (as herein defined), an arylphosphino group (as herein defined) or an aminophosphino group (as herein defined); and R" and R"' of the aminophosphine are the same or different and each is an alkyl group, an aryl group, an alkylaryl group or a cycloalkyl group at least one of which contains one or more chiral centres.

4. A process for the preparation of a transition metal complex as claimed in claim 1, which comprises reacting an optically-active aminophosphine containing at least one chiral centre with a coordination compound of a transition metal.

5. A process according to claim 4, wherein the molar ratio of aminophosphine to transition metal compound is from 1:1 to 15: 1, expressed as the ratio between the phosphorus atoms and transition metal atoms.

6. A process according to claim 4 or 5, wherein the reaction is carried out in a solvent which is an aromatic hydrocarbon, an aliphatic hydrocarbon, an alcohol, an ether, a ketone, an ester, an amide or a mixture of two or more thereof.

7. A process according to claim 4, substantially as described in any one of the foregoing Examples.

8. A transition metal complex whenever prepared by the process claimed in any of claims 4 to 7.

9. A process for the asymmetrical hydrogenation of a prochiral or racemic ethylenically unsaturated compound, which comprises contacting the compound with a complex as claimed in any of claims I to 3 and 8.

10. A process for the asymmetrical hydrogenation of a compound containing a CO and/or CN group, which comprises contacting the compound with a complex as claimed in any of claims 1 to 3 and 8.

11. A process according to claim 9 or 10, wherein the molar ratio of compound to complex is from 10,000:1 to 10:1.

12. A process according to any of claims 9 to 11, wherein the contacting is effected at a temperature of from -70 to 2000 C.

13. A process according to claim 12, wherein the contacting is effected at a temperature of from 0 to 500 C.

14. A process according to any of claims 9 to 13, wherein the contacting is effected under a hydrogen pressure of from 1 to 100 atmospheres.

15. A process according to claim 9, substantially as described in any one of the foregoing Examples I to 10.

16. A process according to claim 10, substantially as described in any one of

the foregoing Examples 11 to 14.

17. The product of a process as claimed in any of claims 9 to 16.