Studies towards the functionalization of light alkanes: Facile C-H bond activation by a neutral Pt(II) alkyl complex

Abstract

Recently our group and the Tilset group reported the activation of R-H bonds by electrophilic platinum cations of the type [(N-N)PtMe]+ (N-N= α-diimine) to generate [(N-N)PtR]+ and methane, a model for the initial step in the so-called Shilov system. The next step involves the oxidation of the resulting Pt(II) alkyl complex. Unfortunately, cationic Pt(II) alkyls are incompatible with the mild oxidizing agents necessary for catalytic turnover. Therefore, a neutral Pt(II) complex which could activate C-H bonds was desirable. The activation of C-H bonds by a neutral Pt(II) complex was achieved by replacing the a-diimine ancillary ligands with mono-anionic X-L type ligands. The addition of pyrrole-2- imines to [(SMe_2)PtMe_2]_2 in benzene results in the formation of a Pt(II) phenyl complex concomitant with evolution of methane (eq. 1). The scope and limitations of the C-H activation step and the subsequent oxidation chemistry will be discussed.