NEUTRAL RHODIUM(I) AMINOPHOSPHINE-PHOSPHINITE COMPLEXES - SYNTHESIS, STRUCTURE, AND USE IN CATALYTIC ASYMMETRIC HYDROGENATION OF ACTIVATED KETO COMPOUNDS - CRYSTAL-STRUCTURE OF [(S)-1-(DICYCLOHEXYLPHOSPHINO)-2-(((DICYCLOHEXYLPHOSPHINO)OXY)METHYL)-PYRROLIDINE](2,4-PENTANEDIOMATO-O,O')RHODIUM(I)

Aminophosphine-phosphinite ligands (AMPP) derived from (S)-2-(hydroxymethyl)pyrrolidine ((S)-R,R'-ProNOP; la-c, 5a-f(R, R' = cyclohexyl, cyclopentyl, 2-propyl, phenyl)) and (S)-1-(methylamino)-2-propanol ((S)-R,R'-isoAlaNOP; 2a,b, 6a-c (R, R' = cyclohexyl, cyclopentyl, phenyl)) have been prepared in high yields and reacted with rhodium precursors to prepare neutral AMPP-rhodium(I) complexes 7-10 of the general formula [RhX(AMPP)](n), where X = Cl, n = 2 or X = acac, eta(5)-C5H5, n = 1. The crystal structure of [Rh(acac){(S)-Cy,Cy-ProNOP}] ((S)-10) has been determined. The compound crystallizes in the triclinic space group P1 with a = 11.459(3) Angstrom, b = 15.980(4) Angstrom, c = 21.684(7) Angstrom, alpha = 75.17(2)degrees, beta = 81.73(2)degrees, gamma = 69.15(2)degrees, and Z = 4. The rhodium atom has a cis square-planar coordination, and the seven-membered metallacycle is in a distorted lambda boat-type conformation with the nitrogen atom in the mean plane RhP2. Complexes 7-10 have been used as catalyst precursors for the asymmetric hydrogenation of dihydro-4, 4-dimethyl-2,3-furandione and N-benzylbenzoylformamide, giving the corresponding hydrogenated products in excellent yields and with fair to good enantiomeric excess (20-89% and 39-88% ee, respectively). Catalytic activities (TOF at 50% conversion at room temperature up to 850 and 1500 h(-1), respectively) as well as enantioselectivities depended strongly on the nature of the substituents at the phosphorus atoms. The dinuclear chlororhodium complex of (S)-Cp,-Cp-isoAlaNOP afforded (S)-pantolactone in 89% ee, whereas the corresponding (S)-Ph,Cp-isoAlaNOP rhodium complex yielded the R enantiomer in 81% ee. A similar inversion of the configuration of the hydrogenated product of N-benzylbenzoylformamide was also observed with these complexes. By varying the nonchiral ligand bound to rhodium as well as the reaction temperature, we observed marked effects on the efficiency of the catalysis. The results suggest that both catalytic activity and enantioselectivity of the [RhX(AMPP)](n), complexes are mainly governed by the aminophosphine moiety of the ligand.