Optically active transition metal complexes. Part 131. Synthesis and epimerization of chiral-at-metal (η 6-arene)ruthenium(II) and (η 6-arene)osmium(II) half-sandwich complexes

Abstract

Ortho-metalated derivatives of the optically active ligand ( S)-(−)- N, N-dimethyl(1-phenylethyl)amine ( LL*-H) react with [(η 6- p-cymene)MCl 2] 2 (M=Ru, Os) to give the half-sandwich complexes [(η 6- p-cymene)Ru( LL*)Cl] ( 1a, b) and [(η 6- p-cymene)Os( LL*)Cl] ( 2a, b). In both cases two diastereomers ( R M, S C) and ( S M, S C) arise differing only in the metal configuration. On crystallization the ( R M, S C)-isomers of both complexes 1 and 2 were obtained diastereomerically pure. The absolute configurations were established by X-ray structure analyses. Epimerization studies clearly showed that the metal configuration in both complexes is labile in solution.