PENTAMETHYLCYCLOPENTADIENYL RUTHENIUM(II) COMPLEXES CONTAINING CHIRALDIPHOSPHINES - SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL-BEHAVIOR - X-RAY STRUCTURE OF (ETA(5)-C5ME5)RU((S,S)-PH2PCH(CH3)CH(CH3)PPH2)CL

Some pentamethylcyclopentadienyl ruthenium(II) diphosphine chloride co mplexes have been prepared by ligand exchange starting with the parent triphenylphosphine derivatives and their reactivities compared with t hose of the corresponding cyclopentadienyl compounds. The pentamethyl ligand causes a greater extent of asymmetric induction when the (R)-pr ophos and (R)-phenphos ligands are used as well as a higher lability o f the stereochemistry at the stereogenic ruthenium centre. A shift of about 200 mV in the oxidation potential is caused by the substitution at the penta-hapto ligand. The order of basicity of the diphosphine li gands was also evaluated and was found to be consistent with previous determinations. The crystal structure of(eta(5)-C5Me5)Ru {(S,S)-chirap hos}Cl shows a coordination around the ruthenium atom similar to that found for the (eta(5)-C5H5)Ru{(S,S) -chiraphos}Cl complex. (C) 1998 El sevier Science S.A. All rights reserved.