Phospholane salts and their use in enantioselective hydrogenation

A process for preparing a catalyst solution which comprises reacting metal complexes and diphosphines in the presence of an inert organic solvent, wherein

• a) an uncharged or cationic metal complex having a TM8 metal as central atom, and
• b) a salt of a chiral ditertiary diphosphine which has one or two phospholane groups which are bound to a carbon chain having from 2 to 4 carbon atoms and contain anions selected from the group consisting of RcCOO−, RcSO3−, BF4−, PF6−, AsF6−, SbF6−, B(C6F5)4− and B(3,5-bistrifluoromethylphenyl)4−, are reacted with one another, where the ratio of the components a) and b) is from 1:1 to 1:2,
• Rc is C1-C6-haloalkyl, C5-C10-halocycloalkyl or C6-C10-haloaryl, and
• wherein the metal complex used as component a) corresponds to one of the formulae:
• [M(diene)2]X, [M(ene)2A]2, [M(diene)A]a, [M(diene)L2]X, [MILbA] and [RuCl2B)]2, [RuL3A]X, [Ru(diene)(carboxylate)2]2,
• wherein M is Rh or Ir,
• diene is a linear or cyclic diolefin,
• ene is an olefin,
• X is an anion selected from the group consisting of BF4−, PF6−, SbF6−, C3COO−, CF3COO−, CH3SO3− and CF3SO3−,
• A is an anionic ligand selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl, acetylacetonate, tetramethylheptanedionate, hydride and chloride,
• a is 0 or 1,
• b is 2, 3 or 4,
• L is an uncharged ligand selected from the group consisting of CO, CH3CN, PhCN, DMSO, pyridine, substituted pyridine and PR3, where R is alkyl, substituted alkyl, aryl, substituted aryl, heteroaryl or substituted heteroaryl,
• carboxylate is the salt of a lower C1-C8-carboxylic acid, and
• B is benzene or alkyl-substituted benzene, and
• wherein the component b) is a phospholane salt of the formula (I) or (II):
• wherein
• R1=R4 and are each OH, alkyl, aryl, aralkyl, alkoxy, aryloxy or aralkyloxy;
• R2 and R3 are each, independently of one another, H, OH, alkyl, aryl, aralkyl, alkoxy, aryloxy or aralkyloxy;
• or R2 and R3 together form part of a cycloaliphatic, cycloheteroaliphatic, aromatic or heteroaromatic ring;
• Ra, Rb are each, independently of one another, a monovalent hydrocarbon radical which has from 1 to 22 carbon atoms and is unsubstituted or substituted, or the two hydrocarbon radicals together with the P atom can form a 3- to 8-membered ring;
• Z is a chain comprising from 2 to 4 carbon atoms which may be part of a 1,2-aryl, 1,2-heteroaryl, 1,2-cycloalkyl, 1,2-heterocycloalkyl ring or a 1,1′-bisarylene or 1,1′-bisheteroarylene;
• and
• X− is an anion RcCOO−, RcSO3−, where Rc=C1-4-alkyl, C5-10-cycloalkyl, or C6-10aryl, in each case substituted by halogen atoms, BF4−, PF6−, AsF6−, SbF6−, B(C6F5)4− or B(3,5-bistrifluoromethylphenyl)4−, with the proviso that the compounds 1,2-bis(2,5-dimethylphospholanyl)benzene tetrafluoroborate and 1,2-bis(2,5-dimethylphospholanyl)benzene bistetrafluoroborate are excluded.