Reductive Elimination and Dissociative β-Hydride Abstraction from Pt(IV) Hydroxide and Methoxide Complexes

The platinum(IV) hydroxide and methoxide complexes fac-(dppbz)PtMe3(OR) (dppbz = o-bis(diphenylphosphino)benzene; R = H (1), CH3 (2)) have been prepared and characterized. Thermolysis of hydroxide 1 produces (dppbz)PtMe2 (3) and methanol in a rare example of directly observed sp(3) carbon-oxygen reductive elimination from a metal center to form an alcohol. Competitive carbon-carbon reductive elimination to form (dppbz)PtMe(OH) (5) and ethane also occurs. In contrast, the major reaction observed upon thermolysis of the methoxide analog 2 is neither carbon-oxygen nor carbon-carbon reductive elimination. Instead, products expected from formal [I-hydride elimination followed by carbon-hydrogen reductive elimination are detected. Mechanistic studies suggest the operation of an alternative mechanism to that most commonly accepted for this fundamental reaction; a dissociative beta-hydride abstraction pathway is proposed.