Mechanism of Me–Re Bond Addition to Platinum(II) and Dioxygen Activation by the Resulting Pt–Re Bimetallic Center

Unusual cis-oxidative addition of methyltrioxorhenium (MTO) to [PtMe₂(bpy)], (bpy = 2,2′-bipyridine) (<b>1</b>) is described. Addition of MTO to <b>1</b> first gives the Lewis acid–base adduct [(bpy)­Me₂Pt–Re­(Me)­(O)₃] (<b>2</b>) and subsequently affords the oxidative addition product [(bpy)­Me₃PtReO₃] (<b>3</b>). All complexes <b>1</b>, MTO, <b>2</b>, and <b>3</b> are in equilibrium in solution. The structure of <b>2</b> was confirmed by X-ray crystallography, and its dissociation constant in solution is 0.87 M. The structure of <b>3</b> was confirmed by extended X-ray absorption fine structure and X-ray absorption near-edge structure in tandem with one- and two-dimensional NMR spectroscopy augmented by deuterium and ¹³C isotope-labeling studies. Kinetics of formation of compound <b>3</b> revealed saturation kinetics dependence on [MTO] and first-order in [Pt], complying with prior equilibrium formation of <b>2</b> with oxidative addition of Me–Re being the rate-determining step. Exposure of <b>3</b> to molecular oxygen or air resulted in the insertion of an oxygen atom into the platinum–rhenium bond forming [(bpy)­Me₃PtOReO₃] (<b>4</b>) as final product. Density functional theory analysis on oxygen insertion pathways leading to complex <b>4</b>, merited on the basis of Russell oxidation pathway, revealed the involvement of rhenium peroxo species