One-Electron Oxidation of [M(PtBu3)2] (M=Pd, Pt): Isolation of Monomeric [Pd(PtBu3)2]+ and Redox-Promoted C-H Bond Cyclometalation

Abstract

Oxidation of zero-valent phosphine complexes [M(PtBu3)2] (M=Pd, Pt) has been investigated in 1,2-difluorobenzene solution using cyclic voltammetry and subsequently using the ferrocenium cation as a chemical redox agent. In the case of palladium, a mononuclear paramagnetic PdI derivative was readily isolated from solution and fully characterized (EPR, X-ray crystallography). While in situ electrochemical measurements are consistent with initial one-electron oxidation, the heavier congener undergoes C-H bond cyclometalation and ultimately affords the 14 valence-electron PtII complex [Pt(κ2PC-PtBu2CMe2CH2)(PtBu3)]+ with concomitant formation of [Pt(PtBu3)2H]+. Uncharted territory: The reaction chemistry of palladium and platinum complexes bearing a +I formal oxidation state has been accessed through one-electron oxidation of [M0(PtBu3)2] (M=Pd, Pt) using [Fc][PF6].