Rhodium and ruthenium complexes of methylene-bridged, P -stereogenic, unsymmetrical diphosphanes.

Enantiopure P -stereogenic methylphosphane-boranes ( S P )-P(BH 3 )PhArMe ( ArMe ; Ar = 1-naphthyl (NpMe), and 2-biphenylyl (BiphMe)) have been used to prepare diphosphanes of the type ArPhPCH 2 PR 2 (R = Ph, iPr or t Bu; ArR ). The ligands have been reacted with [Rh(COD) 2 ]BF 4 to furnish the corresponding six monochelated [Rh(COD)( ArR )]BF 4 organometallic compounds (RhArR) or, depending on the reaction conditions, the bis(chelated) coordination compound [Rh( BiphiPr ) 2 ]BF 4 as a mixture of cis and trans isomers. The crystal structure of cis -[Rh( BiphiPr ) 2 ]BF 4 was obtained. The coordination of the BiphR with [RuCl(μ-Cl)(η 6 - p -cymene) 2 ] 2 under different conditions produced cationic chelated complexes of the type [RuCl(η 6 - p -cymene)(κ 2 - BiphR )]PF 6 (RuBiphR) and the neutral monocoordinated complex [RuCl 2 (η 6 - p -cymene)(κ 1 - BiphPh )] (RuBiphPh') with the uncoordinated P -stereogenic moiety. The Rh(I) complexes were used in the catalytic hydrogenation of functionalized olefins and the Ru(II) complexes were tested in the transfer hydrogenation of acetophenone. Both precursors displayed good activities with moderate enantioselectivities.