Preparation and structural characterization of Os 2Cl 4(Ph 2Ppy) 2(O 2CCH 3): A mixed-ligand compound with an Os 5+2 core and a bond order of 2.5

Abstract

Dichlorotetraacetatodiosmium(III) reacts with 2-(diphenylphosphino)pyridine (abbreviated Ph 2Ppy) in the presence of trimethylsilyl chloride to yield the title compound ( 1) as determined by X-ray crystallography. The molecule contains a cisoid arrangement of two Ph 2Ppy ligands which are distorted from the ideal eclipsed conformation by 30°. A single bridging acetate is also present, and it is twisted about the dimetal unit by 34°. The OsOs distance of 2.395(1) Å, representing a formal bond order of 2.5, is the longest distance reported for a diosmium multiple bond. An investigation of the electrochemistry of 1 by cyclic voltammetry reveals two processes: a reversible oxidation at E 1 2 = +0.95 V and a quasi-reversible reduction at E 1 2 = −0.34 V vs Ag-AgCl.