C–H Bond Activation ofMethane with Gaseous [(CH3)Pt(L)]+ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

Abstract

Electrospray ionization of solutions of dimethyl(1,5-cyclooctadiene)platinum(II) in methanol with traces of nitrogen-containing ligands L provides gaseous complexes of the type [(CH3)Pt(L)]+ with L = pyridine (py), 2,2′-bipyridine (bipy), and 1,10-phenanthroline (phen). These [(CH3)Pt(L)]+ cations are capable of activating the C-H bond in methane as shown by H/D exchange when using CD4 as a neutral reactant. Most reactive is the complex [(CH3)Pt(py)]+ bearing a monodentate nitrogen ligand. The cationic complexes [(CH3)Pt(bipy)]+ and [(CH3)Pt(phen)]+ also bring about activation of methane, though at a lower rate, whereas the bipyridine complex [(CH3)Pt(py)2]+ does not react with methane at thermal conditions. A detailed analysis of the experimental data by means of kinetic modeling provides insight into the underlying mechanistic steps, but a distinction whether the reaction occurs as σ bond metathesis or via an oxidative addition cannot be made on the basis of the experimental data available.