WO2007020221A2

WO2007020221A2 - Amino-phosphinoalkyl-ferrocenes and their use as ligands in catalysts for asymmetric reactions

Info

Publication number: WO2007020221A2
Application number: PCT/EP2006/065197
Authority: WO
Inventors: Antonio Togni; Andreas Bertogg; Ulrike Nettekoven; Mauro Perseghini
Original assignee: Solvias Ag
Priority date: 2005-08-12
Filing date: 2006-08-10
Publication date: 2007-02-22
Also published as: WO2007020221A3

Abstract

Compounds of the formulae (I) and (V) in the form of racemates, mixtures of stereoisomers or optically pure stereoisomers, where R is unsubstituted or F-, Cl-, OH-, C1-C4-alkyl- or C1-C4-alkoxy-subsituted C1-C8-alkyl, C3-C8-cycloalkyl-C1-C4-alkyl or C7-C11 i-aralkyl; X1 is a secondary phosphino group; Ri is C1-C4-alkyl or phenyl; and n is 0 or from 1 to 5. The compounds are ligands for the formation of catalytically active metal complexes as asymmetric, homogeneous catalysts.

Description

Amino-phosphinoalkyl-ferrocenes

The present invention relates to 1-(1'-sec-phosphinoalk-1'-yl)-2-aminoferrocenes, a process for preparing them; N,N'-bis[2-(1-sec-phosphinoalkyl)ferro∞n-1-yl]formamidines, a process for preparing them; metal complexes of transition metals with these compounds as ligands; and the use of the metal complexes as asymmetric catalysts in enantioselective addition reactions onto prochiral organic compounds.

Chiral ferrocenediphosphines having a secondary phosphino group and a i-(sec-phosphino)- alk-1-yl group in the ortho positions of one cyclopentadienyl ring (Cp) of ferrocene have already been described as ligands for metal complexes for asymmetric synthesis, in particular the enantioselective hydrogenation of prochiral organic compounds, in the US patents 5,463,097, 5,466,844 and 5,583,241. They can correspond to the formula

where s-Phos is sec-phoshino. Compounds in which the s-Phos bound to the Cp ring in the above formula has been replaced by an amino group are not known and processes for preparing such compounds have not been described. Such compounds can have properties which are of interest with regard to possible chiral ligands and there is interest in making them available.

It has now surprisingly been found that 1-(1'-sec-phosphinoalk-1'-yl)-2-aminoferrocenes can be obtained in a few process steps starting from 1-vinyl-2-carboxylferrocene. It has also surprisingly been found that 1-(1'-sec-phosphinoalk-1'-yl)-2-aminoferrocenes are themselves chiral ligands for the formation of metal complexes which can be used as catalysts in asymmetric syntheses such as hydrogenations, with good catalytic properties in respect of activity and selectivity being observed. In addition, it has surprisingly been found that these 1-(1'-sec-phosphinoalk-1'-yl)-2-aminoferrocenes can be converted in a simple manner into N,N'-bis[2-(1-sec-phosphinoalkyl)ferrocen-1-yl]formamidines which can in turn be used, as described above, as chiral ligands.

The invention firstly provides compounds of the formula I in the form of racemates, mixtures of stereoisomers or optically pure stereoisomers,

where

R is unsubstituted or F-, Cl-, OH-, C_rC₄-alkyl- or C_rC₄-alkoxy-substituted Ci-C₈-alkyl, C₃-C₈- cycloalkyl, C₃-C₈-cycloalkyl-Ci-C₄-alkyl or C₇-Ci i-aralkyl; Xi is a secondary phosphino group; Ri is Ci-C₄-alkyl or phenyl; and n is 0 or from 1 to 5.

A Ci-C₈-alkyl radical R can be linear or branched and an alkyl radical Ri is preferably d-C₄- alkyl. The radical can be, for example, methyl, ethyl, n- or i-propyl or n- or i-butyl or the isomers of pentyl, hexyl, heptyl and octyl. Examples of substituted alkyl are fluoromethyl, difluoromethyl, trifluoromethyl, trifluoroethyl, hydroxymethyl, β-hydroxyethyl, methoxymethyl, ethoxymethyl and β-methoxyethyl. The alkyl is preferably linear. An alkyl radical Ri is preferably methyl or ethyl.

A cycloalkyl radical R is preferably C₅-C₈-cycloalkyl, preferably C₅-C₆-cycloalkyl. It can be, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl, each of which may, for example, be substituted by F, C_rC₄-alkyl or C_rC₄-alkoxy. Preferred cycloalkyl radicals are cyclopentyl and cyclohexyl.

A cycloalkylalkyl radical R is preferably C₅-C₈-cycloalkyl-Ci-C₂-alkyl. It can be, for example, cyclopropylmethyl or cyclopropylethyl, cyclobutylmethyl or cyclobutylethyl, cyclopentyl methyl or cyclopentylethyl, cyclohexyl methyl or cyclohexylethyl, cycloheptylmethyl or cycloheptyl- ethyl or cyclooctyl methyl or cyclooctylethyl, each of which may, for example, be substituted by F, Ci-C₄-alkyl or Ci-C₄-alkoxy. Preferred cycloalkylalkyl radicals are cyclopentylmethyl and cyclohexylmethyl.

An aralkyl radical R is preferably benzyl or β-phenylethyl, where the phenylethyl group may be substituted by F, Cl, Ci-C₄-alkyl or Ci-C₄-alkoxy. In a particularly preferred embodiment, R in the compounds of the formula I is methyl.

The secondary phosphino group Xi can contain two identical or two different hydrocarbon radicals. In the latter case, the secondary phosphino groups are P-chiral. The secondary phosphino group Xi preferably contains two identical hydrocarbon radicals.

The hydrocarbon radicals can be unsubstituted or substituted and/or contain heteroatoms selected from the group consisting of O, S and N. They can contain from 1 to 22, preferably from 1 to 18 and particularly preferably from 1 to 14, carbon atoms. A preferred secondary phosphino group is one which contains two identical or different radicals selected from the group consisting of linear or branched Ci-Ci₂-alkyl; unsubstituted or d-C₆-alkyl- or CrC₆- alkoxy-substituted C₅-Ci₂-cycloalkyl or C₅-Ci₂-cycloalkyl-CH₂-; phenyl, naphthyl, furyl and benzyl; and phenyl and benzyl substituted by halogen (for example F, Cl and Br), CrC₆-alkyl, Ci-C₆-haloalkyl (for example trifluoromethyl), Ci-C₆-alkoxy, C_rC₆-haloalkoxy (for example trifluoromethoxy), (C₆Hs)₃Si, (Ci-Ci₂-alkyl)₃Si, secondary amino or -CO₂-Ci -C₆-alkyl (for example -CO₂CH₃).

Examples of alkyl substituents on P, which preferably contain from 1 to 6 carbon atoms, are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl and the isomers of pentyl and hexyl. Examples of unsubstituted or alkyl-substituted cycloalkyl substituents on P are cyclopentyl, cyclohexyl, methylcyclopentyl and ethylcyclopentyl, dimethylcyclopentyl, methylcyclohexyl and ethylcyclohexyl and dimethylcyclohexyl. Examples of alkyl-, alkoxy-, haloalkyl-, haloalkoxy- and halogen-substituted phenyl and benzyl substituents on P are o-, m- or p- fluorophenyl, o-, m- or p-chlorophenyl, difluorophenyl or dichlorophenyl, pentafluorophenyl, methyl phenyl, dimethyl phenyl, trimethylphenyl, ethylphenyl, methyl benzyl, methoxyphenyl, dimethoxyphenyl, trifluoromethylphenyl, bistrifluoromethylphenyl, tristrifluoromethylphenyl, trifluoromethoxyphenyl, bistrifluoromethoxyphenyl and 3,5-dimethyl-4-methoxyphenyl.

Preferred secondary phosphino groups are ones which contain identical radicals selected from the group consisting of CrC₆-alkyl, unsubstituted cyclopentyl or cyclohexyl and cyclopentyl or cyclohexyl substituted by from 1 to 3 C_rC₄-alkyl or C_rC₄-alkoxy groups, benzyl and in particular phenyl which may each be unsubstituted or substituted by from 1 to 3 C_rC₄-alkyl, C_rC₄-alkoxy, F, Cl, C_rC₄-fluoroalkyl or C_rC₄-fluoroalkoxy groups. The substituent F can also be present four or five times. The secondary phosphino group Xi preferably corresponds, independently of one another, to the formula -PR₂R₃, where R₂ and R₃ are each, independently of one another, a hydrocarbon radical having from 1 to 18 carbon atoms which is unsubstituted or substituted by halogen, Ci-C₆-alkyl, CrC₆-haloalkyl, CrC₆-alkoxy, CrC₆-haloalkoxy, (Ci-C₄-alkyl)₂amino, (C₆Hs)₃Si, (C_rCi₂-alkyl)₃Si or -CO₂-Ci -C₆-alkyl and/or contains heteroatoms O.

R₂ and R₃ are preferably identical radicals selected from the group consisting of linear or branched Ci-C₆-alkyl, unsubstituted cyclopentyl or cyclohexyl and cyclopentyl or cyclohexyl substituted by from one to three Ci-C₄-alkyl or Ci-C₄-alkoxy groups, furyl, norbomyl, adamantyl, unsubstituted benzyl and benzyl substituted by from one to three d-C₄-alkyl or Ci-C₄-alkoxy groups and in particular unsubstituted phenyl and phenyl substituted by from one to three C_rC₄-alkyl, C_rC₄-alkoxy, -NH₂, -N(C_rC₆-alkyl)₂, OH, F, Cl, C_rC₄-fluoroalkyl or Ci-C₄-fluoroalkoxy groups.

R₂ and R₃ are particularly preferably identical radicals selected from the group consisting of Ci-C₆-alkyl, cyclopentyl, cyclohexyl, furyl and unsubstituted phenyl and phenyl substituted by from one to three CrC₄-alkyl, Ci-C₄-alkoxy and/or Ci-C₄-fluoroalkyl groups.

The secondary phosphino group Xi can be cyclic sec-phosphino groups, for example groups of the formulae

which are unsubstituted or substituted by one or more substituents selected from among -OH, Ci-C₈-alkyl, C₄-C₈-cycloalkyl, C_rC₆-alkoxy, Ci-C₄-alkoxy-C_rC₄-alkyl, phenyl, C_rC₄- alkylphenyl, CrC₄-alkoxyphenyl, benzyl, CrC₄-alkylbenzyl, CrC₄-alkoxybenzyl, benzyloxy, C_rC₄-alkylbenzyloxy, C_rC₄-alkoxybenzyloxy and C_rC₄-alkylidenedioxyl.

The substituents can be bound in one or both α positions relative to the P atom in order to introduce chiral carbon atoms. The substituents in one or both α positions are preferably Ci-C₄-alkyl or benzyl, for example methyl, ethyl, n- or i-propyl, benzyl or -CH₂-O-Ci -C₄-alkyl or -CH₂-O-C₆-Ci o-aryl. Substituents in the β,γ positions can be, for example, Ci-C₄-alkyl, d-C₄-alkoxy, benzyloxy or -0-CH₂-O-, -O-CH(Ci-C₄-alkyl)-O-, -O-C(Ci-C₄-alkyl)₂-O- and -O-CH(C₆-Ci₀-aryl)-O-. Some examples are methyl, ethyl, methoxy, ethoxy, -O-CH(phenyl)-O-, -O-CH(methyl)-O- and -O-C(methyl)₂-O-.

An aliphatic 5- or 6-membered ring or benzene can be fused onto two adjacent carbon atoms in the radicals of the above formulae.

Other known and suitable secondary phosphino radicals are those of cyclic and chiral phospholanes having seven carbon atoms in the ring, for example those of the formulae

where the aromatic rings may be substituted by CrC₄-alkyl, CrC₄-alkoxy, CrC₄-alkoxy- CrC₂-alkyl, phenyl, benzyl, benzyloxy or Ci-C₄-alkylidenedioxyl or C_rC₄-alkylenedioxyl (see US 2003/0073868 A1 and WO 02/048161).

Depending on the type of substitution and the number of substituents, the cyclic phosphino radicals can be C-chiral, P-chiral or C- and P-chiral.

The cyclic sec-phosphino group can correspond, for example, to the formulae (only one of the possible diastereomers shown),

where the radicals R' and R" are each d-C₄-alkyl, for example methyl, ethyl, n- or i-propyl, benzyl, or -CH₂-O-Ci -C₄-alkyl or -CH₂-O-C₆-Ci ₀-aryl and R' and R" are identical or different. When R' and R" are bound to the same carbon atom, they can also together be C₄-C₅-alkylene.

In a preferred embodiment, Xi in the compounds of the formula I is preferably an acyclic secondary phosphino group selected from the group consisting of -P(Ci-C₆-alkyl)₂, -P(C₅-C₈-cycloal kyl)₂, -P(C₇-Ci₂-bicycloalkyl)₂, -P(o-furyl)₂, -P(C₆H₅J₂, -P[2-(Ci-C₆-alkyl)C₆H₄]_2j -P[3-(Ci-C₆-alkyl)C₆H₄]_2j -P[4-(Ci-C₆-alkyl)C₆H₄]_2j -P[2-(Ci-C₆-alkoxy)C₆H₄]_2j -P[3-(Ci-C₆-alkoxy)C₆H₄]_2j -P[4-(Ci-C₆-alkoxy)C₆H₄]₂, -P[2-(trifluoromethyl)C₆H₄]_2j -P[3-(trifluoromethyl)C₆H₄]_2j -P[4-(trifluoromethyl)C₆H₄]_2j -P[3_J5-bis(trifluoromethyl)C₆H₃]_2j -P[3_J5-bis(Ci-C₆-alkyl)₂C₆H₃]_2j -P[3_J5-bis(Ci-C₆-alkoxy)₂- C₆H₃J₂, -P[3,4,5-tris(Ci-C₆-alkoxy)₂C₆H₂]₂, and -P[3,5-bis(Ci-C₆-alkyl)₂-4-(C_rC₆-alkoxy)C₆H₂]₂ or a cyclic phosphino group selected from the group consisting of

which are unsubstituted or substituted by one or more radicals selected from among d-C₄- alkyl, C_rC₄-alkoxy, Ci-C₄-alkoxy-C_rC₂-alkyl, phenyl, benzyl, benzyloxy, C_rC₄-alkylidene- dioxyl and unsubstituted or phenyl-substituted methylenedioxyl.

Specific examples are -P(CH₃J₂, -P(i-C₃H₇)₂, -P(n-C₄H₉)₂, -P(i-C₄H₉)₂, -P(C₆Hn)₂, -P(norbomyl)₂, -P(o-furyl)₂, -P(C₆H₅J₂, P[2-(methyl)C₆H₄]₂, P[3-(methyl)C₆H₄]₂, -P[4-(methyl)C₆H₄]_2j -P[2-(methoxy)C₆H₄]_2j -P[3-(methoxy)C₆H₄]_2j -P[4-(methoxy)C₆H₄]_2j -P[3-(trifluoromethyl)C₆H₄]_2j -P[4-(trifluoromethyl)C₆H₄]_2j -P[3,5-bis(trifluoronnethyl)C₆H₃]_2j -P[3_J5-bis(methyl)C₆H₃]_2j -P[3_J5-bis(nnethoxy)C₆H₃]_2j -P[3_J4_J5-tri(nnethoxy)C₆H₂]_2j -P[3,5-bis(methyl)₂-4-(nnethoxy)C₆H₂]₂ and radicals of the formulae

where

R' is methyl, ethyl, methoxy, ethoxy, phenoxy, benzyloxy, methoxymethyl, ethoxymethyl or benzyloxymethyl and R" independently has one of the meanings of R'.

In a preferred embodiment of the compounds of the formula I, Ri is preferably methyl, n in formula I is particularly preferably 0, or in other words the Cp ring then contains only hydrogen atoms.

The invention further provides a process for preparing the compounds of the formula I, which is characterized in that a) a compound of the formula Il

(II). where Ri and n are as defined above, and R₄ and R'₄ are each, independently of one another, hydrogen or unsubstituted or F-, Cl-, OH-, C_rC₄-alkyl- or C_rC₄- alkoxy-substituted Ci-C₇-alkyl, C₃-C₈-cycloalkyl, C₆-Ci₀-aryl, C₃-C₈-cycloalkyl- C_rC₃-alkyl or C₇-Ci o-aralkyl or R₄ and R'₄ together form a 3- to 8-membered carbocyclic ring which is unsubstituted or substituted by F, Cl, OH, Ci-C₄-alkyl or Ci-C₄-alkoxy; b) is firstly reacted at elevated temperature with diphenylphosphoryl azide of the formula (C₆H₅O)₂P(O)-N₃ in the presence of at least an equivalent amount of a base, for example a tertiary amine, and subsequently at elevated temperature with an alcohol having from 1 to 20 carbon atoms to form a compound of the formula III,

where R₅ is a hydrocarbon radical of an alcohol having from 1 to 20 carbon atoms, c) the compound of the formula III is reacted at elevated temperature with a secondary phosphine X_rH in acetic acid solvent to form a compound of the formula IV,

d) and the compound of the formula IV is then hydrolysed in aqueous basic medium to form a compound of the formula I.

The R₅-O-C(O)- group is a protective group for the amino group. It can also be removed by methods other than hydrolysis, for example by means of hydrogenolysis. If R₄ and R'₄ together form a carbocyclic ring, it is preferably a 5- or 6-membered ring.

The compounds of the formula Il can be obtained by Hoffmann degradation of the known compound 1-(dimethylamino)alk-1-yl-2-carboxylferrocene [L. Beyer et al. In J. of Organom. Chem. (1998) 561(1-2), pages 199-201] by means of methyl iodide. As an alternative, the known vinylferrocenecarboxylic esters can be converted by means of hydrolysis into the compounds of the formula II. Diphenylphosphoryl azide of the formula (C₆Hs)₂P(O)-N₃ is commercially available.

In process step b), "elevated temperature" preferably means temperatures of up to 150⁰C and more preferably from 50 to 120°C. As tertiary amine, preference is given to using a trialkylamine such as (C_rC₄-alkyl)₃N. Particular preference is given to triethylamine. The amine is preferably used in excess, for example in amounts of up to 2 equivalents and more preferably up to 1.5 equivalents, based on the compound of the formula II. Diphenylphosphoryl azide is used in equimolar amounts or a slight excess, for example up to 1.2 equivalents, based on the compound of the formula II. The reaction is preferably carried out in inert solvents having boiling points in the region of the selected reaction temperature. Examples of solvents are aliphatic and aromatic hydrocarbons (methylcyclohexane, octane, benzene, toluene, xylene), halogenated hydrocarbons (methylene chloride, chloroform, dichloroethane, trichloroethane or tetrachloroethane), ethers (tetrahydrofuran, dioxane, ethylene glycol dimethyl or diethyl ether), carboxylic esters and lactones and carboxamides and lactams (dimethylformamide, N-methyl pyrrol idone). In detail, the reactants and solvents can be mixed at room temperature and then heated. The commencement of the reaction can be recognized by bubble formation (nitrogen gas). When bubble formation ceases, the mixture can be stirred at elevated temperature for a further time. The alcohol is subsequently added at about the same temperature and the mixture is stirred further for some time. To isolate the compound of the formula III formed, the reaction mixture can be cooled, mixed with an organic solvent and water and extracted. As an alternative, sodium azide together with pyridine or triphosgene or an azide donor such as sodium azide can be used in place of diphenylphosphoryl azide. Evaporation of the solvent and, if appropriate, purification in a customary manner gives the desired product in high yields (greater than 70% in unoptimized processes).

The alcohols used in process step b) can be aliphatic, cycloaliphatic, cycloaliphatic-aliphatic, aromatic or araliphatic alcohols, for example CrCi₈- and preferably Ci-Ci₂-alkanols, C₃-Ci₂- and preferably C₃-C₈-cycloalkanols, C₃-Ci₂- and preferably C₃-C₈-cycloalkyl-Ci-C₃-alkanols, phenols and C₇-d₂-aralkanols. The aliphatic and aromatic rings may be substituted by C_rCi₈-alkyl groups. Preference is given to using alcohols which are not volatile at the reaction temperature. Some examples are ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methylcyclohexanol, cyclohexylmethanol, phenol, nonylphenol, benzyl alcohol and β-phenylethanol. Particular preference is given to benzyl alcohol.

The temperature in process step c) can be, for example, from 40 to 120⁰C, more preferably from 40 to 100°C. The secondary phosphine is preferably added in excess, for example in amounts of up to 5 equivalents, based on the compound of the formula III. The compound of the formula IV can, after distilling off acetic acid and excess phosphine, be isolated and purified, for example by means of recrystallization. The product is obtained in high yields and optical purity (de > 98%).

The hydrolysis in process step d) is advantageously carried out using aqueous alkali metal hydroxides. The reaction temperature can be from 50 to 120⁰C. The compound of the formula IV can be suspended in a solvent (for example alcohols such as ethanol, propanol, isopropanol, butanol) and water and a solid alkali metal hydroxide (LiOH, NaOH, KOH) can then be added. The mixture is then stirred at elevated temperature, for example from 50 to 120⁰C, until the hydrolysis is complete. After cooling, the organic phase can be separated off, dried and isolated in a known manner by distilling off the solvent and drying the residue. The compound of the formula I is obtained in high yields and optical purity.

The invention also provides the intermediates of the formulae II, III and IV.

The compounds of the formula I themselves are chiral ligands or they can be converted into formamidines which are likewise valuable ligands. The invention further provides compounds of the formula V in the form of racemates, mixtures of stereoisomers or optically pure stereoisomers,

where n, R₁, R and Xi are as defined above, including the preferred embodiments, and R₆ is H, C_rCi₂-alkyl or C₆-Ci₀-aryl.

The invention also provides a process for preparing the compounds of the formula V, which is characterized in that a compound of the formula I is reacted at elevated temperature with at least equivalent amounts of s-triazine or a carboxylic orthoester. The s-triazine is preferably used in excess, for example in amounts of up to 8 equivalents, based on the compound of the formula IV. The reaction temperature can, for example, be from 50 to 150°C, preferably from 60 to 120°C. The reaction is advantageously carried out in the presence of solvents, for example the abovementioned solvents. Reactions with carboxylic orthoesters are described by E. C. Taylor et al. in J. Org. Chem. 28 (1963), pages 108-1112.

The compounds of the formulae I and V can be used to prepare metal complexes. The metal complexes of the invention are homogeneous catalysts or catalyst precursors which can be activated under the reaction conditions which can be used for asymmetric addition reactions onto prochiral, unsaturated, organic compounds, see E. Jacobsen, A. Pfaltz, H. Yamamoto (Eds.), Comprehensive Asymmetric Catalysis I to III, Springer Verlag, Berlin, 1999, and B. Cornils et al., in Applied Homogeneous Catalysis with Organometallic Compounds, Volume 1 , Second Edition, Wiley VCH-Verlag (2002).

The compounds of the formulae I and V according to the invention are ligands for complexes of metals selected from among the group of TM8 metals, preferably from the group consisting of Ru, Rh and Ir, which are excellent catalysts or catalyst precursors for asymmetric syntheses, for example the asymmetric hydrogenation of prochiral, unsaturated, organic compounds. If prochiral unsaturated organic compounds are used, a very high excess of optical isomers can be induced in the synthesis of organic compounds and a high chemical conversion can be achieved in short reaction times. The achievable enantioselectivites and catalyst activities are excellent. Furthermore, such ligands can also be used in other asymmetric addition or cyclization reactions. The invention further provides complexes of metals selected from among the group of transition metals of the Periodic Table (TMs) with one of the compounds of the formulae I and V as ligand.

Possible metals are, for example, Cu, Ag, Au, Ni, Co, Rh, Pd, Ir, Ru and Pt. Preferred metals are rhodium and iridium and also ruthenium, platinum, palladium and copper.

Particularly preferred metals are palladium, ruthenium, rhodium and iridium.

The metal complexes can, depending on the oxidation number and coordination number of the metal atom, contain further ligands and/or anions. They can also be cationic metal complexes. Such analogous metal complexes and their preparation have been widely described in the literature.

The metal complexes can, for example, correspond to the general formulae Vl and VII

A₃MeL_r (Vl), (A₃MeL_r)^(z+)(E )_z (VII),

where A₃ is one of the compounds of the formulae I and V,

L represents identical or different monodentate, anionic or nonionic ligands, or L represents identical or different bidentate, anionic or nonionic ligands; r is 2, 3 or 4 when L is a monodentate ligand or n is 1 or 2 when L is a bidentate ligand; z is 1, 2 or 3;

Me is a metal selected from the group consisting of Rh, Ir and Ru; with the metal having the oxidation state 0, 1 , 2, 3 or 4;

E^" is the anion of an oxo acid or complex acid; and the anionic ligands balance the charge of the oxidation state 1, 2, 3 or 4 of the metal.

The above-described preferences and embodiments apply to the compounds of the formulae I and V.

Monodenate nonionic ligands can, for example, be selected from the group consisting of olefins (for example ethylene, propylene), solvating solvents (nitriles, linear or cyclic ethers, unalkylated or N-alkylated amides and lactams, amines, phosphines, alcohols, carboxylic esters, sulphonic esters), nitrogen monoxide and carbon monoxide. Suitable polydentate anionic ligands are, for example, allyls (allyl, 2-methallyl), cyclopenta- dienyl or deprotonated 1,3-diketo compounds such as acetylacetonate.

Monodentate anionic ligands can, for example, be selected from the group consisting of halide (F, Cl, Br, I), pseudohalogenide (cyanide, cyanate, isocyanate) and anions of carboxylic acids, sulphonic acids and phosphonic acids (carbonate, formate, acetate, propionate, methylsufonate, trifluoromethylsulphonate, phenylsufonate, tosylate).

Bidentate nonionic ligands can, for example, be selected from the group consisting of linear or cyclic diolefins (for example hexadiene, cyclooctadiene, norbomadiene), dinitriles (malononitrile), unalkylated or N-alkylated carboxylic diamides, diamines, diphosphines, diols, dicarboxylic diesters and disulphonic diesters.

Bidentate anionic ligands can, for example, be selected from the group consisting of anions of dicarboxylic acids, disulphonic acids and diphosphonic acids (for example of oxalic acid, malonic acid, succinic acid, maleic acid, methylenedisul phonic acid and methylenediphosphonic acid).

Preferred metal complexes also include those in which E is -Cl^", -Br^", -I^", CIO₄ ^", CF₃SO₃ ^", CH₃SO₃ ^", HSO₄ ^", (CF₃SO₂J₂N^", (CF₃SO₂)₃C^", tetraaryl borates such as B(phenyl)₄ ^", B[bis(3,5-trifluoromethyl)phenyl]₄ ^", B[bis(3,5-dimethyl)phenyl]₄ ^", B(C₆F₅)₄ ^" and B(4-methylphenyl)₄ ^", BF₄ ^", PF₆ ^", SbCI₆ ^", AsF₆ ^" or SbF₆ ^" .

Particularly preferred metal complexes which are particularly suitable for hydrogenations correspond to the formulae VIII and IX,

[A₃MeY₁Z] (VIII), [A₃MeY₁J⁺E₁ ^" (IX),

where

A₃ is one of the compounds of the formulae I and V;

Me is rhodium or iridium;

Y₁ is two olefins or a diene;

Z is Cl, Br or I; and

E₁ ^" is the anion of an oxo acid or complex acid. The above-described embodiments and preferences apply to the compounds of the formulae I and V.

Olefins Yi can be C₂-Ci₂-olefins, preferably C₂-C₆-olefins and particularly preferably C₂-C₄- olefins. Examples are propene, 1-butene and in particular ethylene. The diene can have from 5 to 12, preferably from 5 to 8, carbon atoms and can be an open-chain, cyclic or polycyclic dienes. The two olefin groups of the diene are preferably connected by one or two CH₂ groups. Examples are 1,4-pentadiene, cyclopentadiene, 1,5-hexadiene, 1,4-cyclohexadiene, 1 ,4- or 1,5-heptadiene, 1,4- or 1,5-cycloheptadiene, 1,4- or 1,5-octadiene, 1,4- or 1,5-cyclo- octadiene and norbomadiene. Y is preferably two ethylenes or 1,5-hexadiene, 1,5-cyclo- octadiene or norbomadiene.

In the formula VIII, Z is preferably Cl or Br. Examples of E₁ are BF₄ ^", CIO₄ ^", CF₃SO₃ ^", CH₃SO₃ ^", HSO₄ ^", B(phenyl)₄ ^", B[bis(3,5-trifluoromethyl)phenyl]₄ ^", PF₆ ^", SbCI₆ ^", AsF₆ ^" or SbF₆ ^".

The metal complexes of the invention are prepared by methods known in the literature (see also US-A-5,371 ,256, US-A-5,446,844, US-A-5,583,241 and E. Jacobsen, A. Pfaltz, H. Yamamoto (Eds.), Comprehensive Asymmetric Catalysis I to III, Springer Verlag, Berlin, 1999, and references cited therein).

Ruthenium complexes can, for example, correspond to the formula X,

[Ru_aH_bZ_c(A₃)_dL_Θ]KE^k)_g(S)_h (X),

where is Z Cl, Br or I; A₃ is a compound of the formula I or V; L represents identical or different ligands; E^" is the anion of an oxo acid, mineral acid or complex acid; S is a solvent capable of coordination as ligand; and a is from 1 to 3, b is from O to 4, c is from O to 6, d is from 1 to 3, e is from O to 4, f is from 1 to 3, g is from 1 to 4, h is from O to 6 and k is from 1 to 4, with the total charge on the complex being zero.

The preferences indicated above for Z, A₃, L and E^" apply to the compounds of the formula X. The ligands L can additionally be arenes or heteroarenes (for example benzene, naphthalene, methyl benzene, xylene, cumene, 1 ,3,5-mesitylene, pyridine, biphenyl, pyrrole, benzimidazole or cyclopentadienyl) and metal salts having a Lewis acid function (for example ZnCI₂, AICI₃, TiCI₄ and SnCI₄). The solvent ligands can be, for example, alcohols, amines, acid amides, lactams and sulphones.

Complexes of this type are described in the literature mentioned below and the references cited therein:

D. J. Ager, S. A. Laneman, Tetrahedron: Asymmetry, 8, 1997, 3327 - 3355;

T. Ohkuma, R. Noyori in Comprehensive Asymmetric Catalysis (E.N. Jacobsen, A. Pfaltz,

H. Yamamoto, Eds.), Springer, Berlin, 1999, 199-246;

J. M. Brown in Comprehensive Asymmetric Catalysis (E.N. Jacobsen, A. Pfaltz,

H. Yamamoto, Eds.), Springer, Berlin, 1999, 122 - 182;

T. Ohkuma, M. Kitamura, R. Noyori in Catalytic Asymmetric Synthesis, 2^nd Edition (I. Ojima,

Ed.), Wiley-VCH New York, 2000, 1 - 110;

N. Zanetti, et al. Organometallics 15, 1996, 860.

The metal complexes of the invention are homogeneous catalysts or catalyst precursors which can be activated under the reaction conditions, which can be used for asymmetric addition reactions onto prochiral, unsaturated, organic compounds.

The metal complexes can, for example, be used for asymmetric hydrogenation (addition of hydrogen) of prochiral compounds having carbon-carbon or carbon-heteroatom double bonds. Such hydrogenations using soluble homogeneous metal complexes are described, for example, in Pure and Appl. Chem., Vol. 68, No. 1 , pages 131-138 (1996). Preferred unsaturated compounds to be hydrogenated contain the groups C=C, C=N and/or C=O. According to the invention, metal complexes of ruthenium, rhodium and iridium are preferably used for the hydrogenation.

The invention further provides for the use of the metal complexes of the invention as homogeneous catalysts for preparing chiral organic compounds, preferably for the asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds.

The invention also provides a process for preparing chiral organic compounds by asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds in the presence of a catalyst, which is characterized in that the addition reaction is carried out in the presence of catalytic amounts of at least one metal complex according to the invention. Preferred prochiral, unsaturated compounds to be hydrogenated can contain one or more, identical or different groups C=C, C=N and/or C=O in open-chain or cyclic organic compounds, with the groups C=C, C=N and/or C=O being able to be part of a ring system or being exocyclic groups. The prochiral unsaturated compounds can be alkenes, cycloalkenes, heterocycloalkenes or open-chain or cyclic ketones, α,β-diketones, α- or β-ketocarboxylic acids or their α,β-keto acetals or ketals, esters and amides, ketimines and kethydrazones.

Some examples of unsaturated organic compounds are acetophenone, 4-methoxyaceto- phenone, 4-trifluoromethylacetophenone, 4-nitroacetophenone, 2-chloroacetophenone, corresponding unsubstituted or N-substituted acetophenonebenzylimines, unsubstituted or substituted benzocyclohexanone or benzocyclopentanone and corresponding imines, imines from the group consisting of unsubstituted or substituted tetrahydroquinoline, tetrahydro- pyridine and dihydropyrrole, and unsaturated carboxylic acids, esters, amides and salts, for example α- and, if appropriate, β-substituted acrylic acids or crotonic acids. Preferred carboxylic acids are those of the formula

Rioi-CH=C(Rio₂)-C(0)OH

and also their salts, esters and amides, where R₁₀₁ is d-C₆-alkyl, unsubstituted C₃-C₈- cycloalkyl or C₃-C₈-cycloalkyl substituted by from 1 to 4 CrC₆-alkyl, C_rC₆-alkoxy or C_rC₆- alkoxy-CrC₄-alkoxy groups, or unsubstituted C₆-Ci₀-aryl, preferably phenyl, or C₆-Ci₀-aryl, preferably phenyl, substituted by from 1 to 4 CrC₆-alkyl, C_rC₆-alkoxy or Ci-C₆-alkoxy-CrC₄- alkoxy groups, and R₁₀₂ is linear or branched CrC₆-alkyl (for example isopropyl) or cyclo- pentyl, cyclohexyl, phenyl or protected amino (for example acetylamino) which may in each case be unsubstituted or be substituted as defined above.

The process of the invention can be carried out at low or elevated temperatures, for example temperatures of from -20 to 150⁰C, preferably from -10 to 100⁰C and particularly preferably from 10 to 8O⁰C. The optical yields are generally better at relatively low temperature than at higher temperatures.

The process of the invention can be carried out at atmospheric pressure or superatmos- pheric pressure. The pressure can be, for example, from 10⁵ to 2x10⁷ Pa (pascal). Hydrogenations can be carried out at atmospheric pressure or under superatmospheric pressure. Catalysts are preferably used in amounts of from 0.0001 to 10 mol%, particularly preferably from 0.001 to 10 mol% and in particular from 0.01 to 5 mol%, based on the compound to be hydrogenated.

The preparation of the ligands and catalysts and the hydrogenation can be carried out without solvents or in the presence of an inert solvent, with one solvent or mixtures of solvents being able to be used. Suitable solvents are, for example, aliphatic, cycloaliphatic and aromatic hydrocarbons (pentane, hexane, petroleum ether, cyclohexane, methylcyclohexane, benzene, toluene, xylene), aliphatic halogenated hydrocarbons (methylene chloride, chloroform, dichloroethane and tetrachloroethane), nitriles (acetonitrile, propionitrile, benzonitrile), ethers (diethyl ether, dibutyl ether, t-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, diethylene glycol monomethyl or monoethyl ether), ketones (acetone, methyl isobutyl ketone), carboxylic esters and lactones (ethyl or methyl acetate, valerolactone), N-substituted lactams (N-methyl- pyrrolidone), carboxamides (dimethylamide, dimethylformamide), acyclic ureas (dimethyl- imidazoline) and sulphoxides and sulphones (dimethyl sulphoxide, dimethyl sulphone, tetramethylene sulphoxide, tetramethylene sulphone) and alcohols (methanol, ethanol, propanol, butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether) and water. The solvents can be used either alone or as a mixture of at least two solvents.

The reaction can be carried out in the presence of cocatalysts, for example quaternary ammonium halides (tetrabutylammonium iodide) (see, for example, US-A-5,371 ,256, US-A-5,446,844 and US-A-5,583,241 and EP-A-O 691 949). The presence of fluorinated alcohols such as 1,1,1-trifluoroethanol can likewise aid the catalytic reaction. Furthermore, the addition of up to equimolar amounts of a base such as an alkali metal hydroxide or alkoxide or carbonate can be advantageous.

The metal complexes used as catalysts can be added as separately prepared, isolated compounds or can also be formed in situ prior to the reaction and then be mixed with the substrate to be hydrogenated. It can be advantageous to add additional ligands in the reaction using isolated metal complexes or to use an excess of the ligands in the in-situ preparation. The excess can be, for example, from 1 to 6 mol, preferably from 1 to 2 mol, based on the metal compound used for the preparation. The process of the invention is generally carried out by initially charging the catalyst and then adding the substrate, if desired reaction auxiliaries and the compound to be added on and subsequently starting the reaction. Gaseous compounds to be added on, for example hydrogen or ammonia, are preferably introduced under pressure. The process can be carried out continuously or batchwise in various types of reactor.

The chiral organic compounds which can be prepared according to the invention are active substances or intermediates for the preparation of such substances, in particular in the field of production of flavours and fragrances, pharmaceuticals and agrochemicals.

The following examples illustrate the invention.

A) Preparation of compounds of the formula I

Abbreviations: Bn is benzyl, Ph is phenyl, Ac is acetyl.

Example A1 : Preparation of (S)-2-[(Yf?)-1-(diphenylphosphino)ethyl]aminoferrocene (A1)

a) Preparation of compound (2)

43.67 ml of methyl iodide (684 mmol, 8 equivalents) are added to a mixture of 25.43 g (85.30 mmol, 1 equivalent) of 1-[(dimethylamino)eth-1'-yl]-2-carboxylferrocene, 94.58 g of K₂CO₃ (684 mmol, 8 equivalents) and 510 ml of acetone. A clear, deep red solution with a light-coloured precipitate (K₂CO₃) is formed. The reaction mixture is stirred for 3.5 hours and is then filtered and the filtrate is evaporated to dryness, giving a red foam-like solid. This is taken up in benzene and stirred at 85°C for 45 minutes. The red oil obtained after filtration and evaporation of the solvent is admixed with ethanol (450 ml), water (450 ml) and sodium hydroxide (10.28 g, 256 mmol, 3 equivalents) and the mixture is stirred at 60°C for 13 hours. The two-phase reaction solution is then admixed at room temperature with fert-butyl methyl ether (TBME) and acidified. The organic phase is dried over MgSO₄, filtered and evaporated, whereupon the desired product is isolated as a yellow, amorphous solid in a yield of 15.99 g (73%). ¹H NMR (CDCI₃, 300.1 MHz): δ = 4.23 (s, 5H), 4.53 (t, 1 H), 4.85 (t, 1 H), 4.95 (dd, 1 H), 4.95 (dd, 1H), 5.22 (dd, 1 H), 5.53 (dd, 1 H). Melting point = 115.5°C.

b) Preparation of compound (3)

9.82 ml (70.3 mmol, 1.5 equivalents) of dry triethylamine and 11.3 ml (51.5 mmol, 1.1 equivalents) of diphenylphosphorγl azide are added in this order to a solution of 11.97 g (46.80 mmol, 1 equivalent) of compound (2) in toluene (68 ml). The clear, deep red solution is stirred for 30 minutes and then heated quickly to 95°C. After 10 minutes, a gas (N₂) begins to be given off. After 30 minutes, 9.70 ml (93.6 mmol, 2.0 equivalents) of benzyl alcohol are added to the reaction mixture and the mixture is stirred at 95°C for a further 5 minutes. After cooling to room temperature, the reaction mixture is extracted with TMBE and water, the organic phase is dried over MgSO₄, filtered and evaporated. The crude product is purified by filtration over passivated aluminium oxide (basic, activity II), giving the product as an amorphous, red solid in a yield of 12.00 g (71%). ¹H NMR (CDCI₃, 300.1 MHz): δ = 4.10 (s, 5H), 4.11 (dd, 1 H), 4.31 (t, 1H), 4.81 (bs, 1 H), 5.18 (dd, 1 H), 5.18 (s, 2H), 5.42 (dd, 1H), 6.02 (bs, 1 H), 6.50 (dd, 1H), 7.32-7.45 (m, 5 H).

c) Preparation of compound (4)

3.86 ml (22.2 mmol, 4 equivalents) of diphenylphosphine are added to a solution of 2.00 g (5.54 mmol, 1 equivalent) of compound (3) in 9.0 ml of dry acetic acid at room temperature. After stirring at 60⁰C for 16 hours and evaporation of the solvent in a high vacuum, the excess diphenylphosphine is distilled off at 80⁰C. The crude product is washed with pentane and recrystallized from isopropanol (i-PrOH). This gives 2.51 g (83%) of a red, crystalline solid. According to ¹H-NMR, the de (diastereomeric excess) is > 98% (no signal of the other diastereomeric compound is observed). ¹H NMR (CDCI₃, 250.1 MHz): δ = 1.55 (q, 3H), 3.25 (dq, 1H), 3.87-3.89 (m, 1H), 3.99 (dd, 1H), 4.12 (s, 5H), 4.59 (bs, 1H), 4.81 (bs, 1 H), 4.98- 5.11 (m, 2H), 6.99-7.18 (m, 5H), 7.31-7.45 (m, 8H), 7.49-7.58 (m, 2H). ³¹P NMR (CDCI₃ 101.3 MHz): δ = 3.4. Melting point = 153.5°C.

d) Preparation of compound A1

A suspension of 2.39 g (4.36 mmol) of compound (4) in 30 ml of i-PrOH and 30 ml of water is degassed with the aid of an ultrasonic bath and then admixed with 16.5 g of potassium hydroxide. The mixture is stirred at 90⁰C for 17 hours and then cooled. A clear, red organic phase and a colourless aqueous phase are obtained. The organic phase is separated off and dried over MgSO₄, then filtered and evaporated. The compound A1 is obtained in the form of a red solid in a yield of 1.66 g (92%). ¹H NMR (C₆D₆ 500.2 MHz): δ = 1.53 (bs, 2H), 1.67 (dd, 3H), 3.59 (dq, 1 H), 3.79 (t, 1 H), 3.83 (t, 1H), 3.89-3.90 (m, 1H), 4.12 (m, 5H), 7.05-7.11 (m, 3H), 7.23-7.29 (m, 3H), 7.33-7.38 (m, 2H), 7.67-7.72 (m, 2H). ³¹P NMR (C₆D₆ 121.5 MHz): δ = 3.9.

B) Preparation of compounds of the formula V

Example B1 : Preparation of N,N'-bis[(S)-2-{(7R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]- formamidine (B1)

a) Preparation of compound (A1)

A suspension of 1.85 g (4.48 mmol) of compound (4) in 30 ml of i-PrOH and 20 ml of water is degassed for 10 minutes with the aid of an ultrasonic bath and then admixed with 11.0 g of potassium hydroxide. The mixture is stirred at 90°C for 12 hours and then cooled. A clear, red organic phase and a clear, colourless aqueous phase are obtained. After separating off the organic phase, drying the organic phase over MgSO₄, filtering and evaporating the solvent, the compound (A1) obtained as an orange-red solid is used directly in the next step.

b) Preparation of compound (B1)

After addition of 2.25 g (27.8 mmol, 6.2 equivalents) of s-triazine and 6.0 ml of dioxane, the mixture is stirred at 90⁰C for 21 hours and then evaporated under reduced pressure with the aid of a distillation apparatus. After purification by column chromatography (200 g of SiO₂, cyclohexane:ethyl acetate:triethylamine = 3:1 :0.04), the compound (B1) is obtained in a yield of 1.42 g (69%).¹H NMR (CDCI₃, 250.1 MHz): δ = 1.54 (q, 6 H), 3.44 (dq, 2 H), 3.93-3.99 (m, 4H), 4.06-4.19 (m, 12 H), 6.86 (s, 1H), 6.99-7.08 (m, 4 H), 7.11-7.19 (m, 4 H), 7.19-7.25 (m, 2H), 7.36-7.43 (m, 6H), 7.50-7.58 (m, 4H). ³¹P NMR (CDCI₃ 101.3 MHz): δ = 6.1.

C) Use examples (hvdrogenations)

Example C1 : Hydrogenation of acetophenone using compound (B1) as ligand

2.93 mg (3.2 μmol) of dichlorotris(diphenylphosphine)ruthenium and 3.0 mg (3.2 μmol) of compound (B1) are placed in a 20 ml glass reaction vessel equipped with magnetic stirrer and septum closure and the vessel is filled with argon. 0.65 ml of isopropanol is subsequently added. After stirring at room temperature for 10 minutes, the mixture is admixed with 0.64 ml (0.64 mmol) of a 1 M solution of acetophenone in isopropanol and 0.64 ml (0.64 mmol) of a 1 M solution of potassium tert-butoxide in isopropanol (ratio of substrate: catalyst = 200). The vessel is transferred to an autoclave and placed under an H₂ pressure of 80 bar. After stirring at room temperature for 16 hours, the autoclave is vented. A sample of the reaction mixture is taken, diluted with acetone for GC analysis, filtered and analysed by gas chromatography. This gives 55% of (S)-i-phenylethanol having an enantiomeric excess (ee) of 44%.

Example C2: Hydrogenation of acetophenone using compound (A1) as ligand A suspension of 19.18 mg (20.0 μmol) of dichlorotetrakis(diphenylphosphine)ruthenium(ll) and 8.52 mg (20.6 μmol) of compound (A1) in 0.5 ml of toluene is stirred at 90°C for 2 hours. 0.25 ml (10 μmol) of this catalyst solution is diluted to 3 ml with toluene, transferred to a 50 ml steel autoclave and admixed with 0.12 ml (1.0 mmol) of acetophenone and 1.0 ml (1.0 mmol) of an aqueous 1 M solution of NaOH (substrate/catalyst ratio = 100). The reaction mixture is stirred at room temperature under a hydrogen pressure of 80 bar for 16 hours. After venting the autoclave, a sample is taken, diluted with acetone for GC analysis and filtered. (S)-I-Phenylethanol is obtained with 100% chemoselectivity and with an enantiomeric excess of 38%.

Example C3: Hydrogenation of dimethyl itaconate using compound (A1) as ligand 0.3 ml (5.8 μmol) of a solution of 59.5 mg of compound (A1) in 7.5 ml of THF is added to 1.41 mg (2.9 μmol) of chlorocyclooctadienerhodium(l) dimer in a 10 ml Schlenk flask and the mixture is diluted with 1.7 ml of THF. After stirring at room temperature for 10 minutes, 94.9 mg (0.60 mmol) of dimethyl itaconate are added and the solution is transferred to a 50 ml autoclave (substrate/catalyst ratio = 100). The reaction mixture is stirred at room temperature under a hydrogen pressure of 9 bar for 18 hours. After venting the autoclave, a sample is taken, diluted with acetone for GC analysis and filtered. Dimethyl (S)-2-methyl- succinate is obtained with 100% chemoselectivity and with an enantiomeric excess of 32%.

Claims

1. Compounds of the formula I in the form of racemates, mixtures of stereoisomers or optically pure stereoisomers,

where

2. Compounds according to Claim 1, characterized in that R is methyl.

3. Compounds according to Claim 1, characterized in that n is 0.

4. Compounds according to Claim 1, characterized in that Xi corresponds, independently of one another, to the formula -PR₂R₃, where R₂ and R₃ are each, independently of one another, a hydrocarbon radical having from 1 to 18 carbon atoms which is unsubstituted or substituted by halogen, CrC₆-alkyl, CrC₆-haloalkyl, CrC₆-alkoxy, CrC₆-haloalkoxy, (C_rC₄- alkyl)₂amino, (C₆H₅)₃Si, (Ci-Ci₂-alkyl)₃Si or -CO₂-Ci -C₆-alkyl and/or contains heteroatoms O.

5. Compounds according to Claim 1, characterized in that Xi is an acyclic secondary phosphino group selected from the group consisting of -P(Ci-C₆-alkyl)₂, -P(C₅-C₈-cycloalkyl)₂, -P(C₇-Ci₂-bicycloalkyl)₂, -P(o-furyl)₂, -P(C₆H₅)₂, -P[2-(Ci-C₆-alkyl)C₆H₄]_2j -P[3-(Ci-C₆-alkyl)C₆H₄]₂, -P[4-(Ci-C₆-alkyl)C₆H₄]₂, -P[2-(Ci-C₆-alkoxy)C₆H₄]₂, -P[3-(Ci-C₆-alkoxy)C₆H₄]₂, -P[4-(Ci-C₆-alkoxy)C₆H₄]₂, -P[2-(trifluoromethyl)C₆H₄]₂, -P[3-(trifluoromethyl)C₆H₄]₂, -P[4-(trifluoromethyl)C₆H₄]₂, -P[3,5-bis(trifluoromethyl)C₆H₃]₂, -P[3,5-bis(Ci-C₆-alkyl)₂C₆H₃]₂, -P[3,5-bis(Ci-C₆-alkoxy)₂C₆H₃]₂, -P[3,4,5-tris(Ci-C₆- alkoxy)₂C₆H₂]₂, and -P[3,5-bis(Ci-C₆-alkyl)₂-4-(Ci-C₆-alkoxy)C₆H₂]₂ or a cyclic phosphino group selected from the group consisting of

which are unsubstituted or substituted by one or more radicals selected from among d-C₄- alkyl, Ci-C₄-alkoxy, Ci-C₄-alkoxy-CrC₂-alkyl, phenyl, benzyl, benzyloxy, C_rC₄-alkylidene- dioxyl and unsubstituted or phenyl-substituted methylenedioxyl.

6. Process for preparing the compounds of the formula I, which is characterized in that a) a compound of the formula Il

where Ri and n are as defined above, and R₄ and R'₄ are each, independently of one another, hydrogen or unsubstituted or F-, Cl-, OH-, Ci-C₄-alkyl- or d-C₄- alkoxy-substituted Ci-C₇-alkyl, C₃-C₈-cycloalkyl, C₆-Ci₀-aryl, C₃-C₈-cycloalkyl- C_rC₃-alkyl or C₇-Ci o-aralkyl or R₄ and R'₄ together form a 3- to 8-membered carbocyclic ring which is unsubstituted or substituted by F, Cl, OH, Ci-C₄-alkyl or Ci-C₄-alkoxy; b) is firstly reacted at elevated temperature with diphenylphosphorγl azide of the formula (C₆H₅O)₂P(O)-N₃ in the presence of at least an equivalent amount of a tertiary amine and subsequently at elevated temperature with an alcohol having from 1 to 20 carbon atoms to form a compound of the formula III,

and the compound of the formula IV is then hydrolysed in aqueous basic medium to form a compound of the formula I.

7. Compounds of the formulae II, III and IV,

where

R, R₁, X₁, and n are as defined in Claim 1 ,

R₄ and R'₄ are each, independently of one another, hydrogen or unsubstituted or F-, Cl-,

OH-, C_rC₄-alkyl- or C_rC₄-alkoxy-substituted C_rC₇-alkyl, C₃-C₈-cycloalkyl, C₆-C₁₀-aryl, C₃-

C₈-CVClOaIkVl-C₁ -C₃-alkyl or C₇-C₁₀-aralkyl or R₄ and R'₄ together form a 3- to 8-membered carbocyclic ring which is unsubstituted or substituted by F, Cl, OH, C_rC₄-alkyl or C₁-C₄- alkoxy, and

R₅ is the hydrocarbon radical of an alcohol containing from 1 to 20 carbon atoms.

8. Compounds of the formula V in the form of racemates, mixtures of stereoisomers or optically pure stereoisomers,

where n, R₁, R and Xi are as defined in Claim 1 and R₆ is H, C_rCi₂-alkyl or C₆-Ci₀-aryl.

9. Process for preparing the compound of the formula V according to Claim 8, characterized in that a compound of the formula I according to Claim 1 is reacted at elevated temperature with at least equivalent amounts of s-triazine.

10. Complexes of metals selected from the group of transition metals of the Periodic Table with one of the compounds of the formulae I and V as ligands.

11. Metal complexes according to Claim 10, characterized in that the metals are selected from the group consisting of Cu, Ag, Au, Ni, Co, Rh, Pd, Ir, Ru and Pt.

12. Use of the metal complexes according to Claim 10 as homogeneous catalysts for the preparation of chiral organic compounds, preferably for the asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds.

13. Process for preparing chiral organic compounds by asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds in the presence of a catalyst, characterized in that the addition reaction is carried out in the presence of catalytic amounts of at least one metal complex according to Claim 10.