SYNTHESIS, SEPARATION, AND STEREOCHEMICAL STUDIES OF CHIRAL-AT-METAL RHODIUM(III) COMPLEXES - CRYSTAL-STRUCTURE OF ETA(5)-C(5)ME(5))RHCL(PH(2)PCH(ME)CH(2)PPH(2))]BF4

The synthesis of chiral-at-metal [(eta(5)-C(5)Me(5))RhX(prophos)]X (pr ophos = (R)-1,2-propanediylbis(diphenylphosphine); X = Cl (2a, 2a'), I (4a)) complexes from [{(eta(5)-C(5)Me(5))RhX)(2)-(mu-X)(2)] in methan ol is reported (de = 54 and greater than or equal to 98, respectively) . The rhodium center is configurationally stable in the iodo complex, but the chloro analogue epimerizes in polar solvents. Complexes 2 and 4 are formed through the dinuclear intermediates [{(eta(5)-C(5)Me(5))R hX(2)}(2)(mu-prophos)] and the monodentate diphosphine complexes [(eta (5)-C(5)Me(5))RhX(2)(prophos)] with high stereoselectivity. The determ ination of the absolute configuration of 2a and 2a' complexes comes fr om the X-ray diffraction study of [(eta(5)-C(5)Me(5))RhCl(prophos)]BF4 (2b) obtained from mixtures of 2a and 2a' by anion exchange. In 2b th e chiral metal exhibits an S absolute configuration.