Preparation and Characterization of cis-.LAMBDA.-[Ru(bpy)2(py)(O)]2+

Abstract

High-oxidation-state oxo complexes of ruthenium with polypyridine ligands such as cis-[Ru(bpy){sub 2}(py)O]{sup 2+} (bpy = 2,2{prime}-bipyridine, py = pyridine) are efficient stoichiometric and catalytic oxidants in a variety of organic and inorganic oxidation reactions. Recently, it was also reported that cis-[Ru(bpy){sub 2}(py)O]{sup 2+} is an efficient DNA cleavage agent. The results of mechanistic studies involving cis-[Ru(bpy){sub 2}(py)(O)]{sup 2+} suggest that oxidation of PPh{sub 3} to Ph{sub 3}PO or (CH{sub 3}){sub 2}S to (CH{sub 3}){sub 2}SO occurs by O atom transfer in oxidation of alcohols to aldehydes may occur by hydride transfer and oxidation of hydroquinones occurs by proton-coupled electron transfer. The complex cis-[Ru(bpy){sub 2}(py)(O)]{sup 2+} and its reduced form, cis-[Ru(bpy){sub 2}(py)(H{sub 2}O)]{sup 2+}, are chiral at the metal center. Stereoselective oxygen atom transfer from the chiral oxidant to an organic substrate is a possibility. Most well-studied asymmetric oxidation reactions of this sort are dependent on the selectivity of chiral ligands. Stereoselective oxidation directly involving the chiral metal center has not been studied extensively although the topic has been addressed. In this paper, the preparation and characterization of optically active cis-[Ru(bpy){sub 2}(py)(O)]{sup 2+} from optically active cis-[Ru(bpy){sub 2}(py)(H{sub 2}O)]{sup 2+} and the asymmetric oxidation of methyl p-tolyl sulfide by this chiralmore » oxidant to chiral sulfoxide are reported.« less