Carbon-hydrogen bond activation mediated by cationic platinum(II) complexes
Transition metal catalyzed hydrocarbon functionalization is of current interest to chemical and petroleum industries. The so-called "Shilov System", comprised of aqueous solutions of Pt(II) and Pt(IV) chlorides. converts simple alkanes, including methane, to alcohols and alkyl chlorides. The C-H activation step appears to dictate both the selectivity and the overall reaction rates of these transformations. Consequently, we have been trying to gain more insights through studying model systems. A series of diaryldiimine-ligated cationic Pt(II) methyl complexes are synthesized. These compounds show high reactivity towards hydrocarbons, and the reactions are accelerated by both increased electron density and decreased steric bulk on metal centers. The reactions appear to proceed through a solvent-assisted associative pathway. The substrate regioselectivity depends on the steric bulk of both the substrates and the metal centers.