C-H Bond Activation with Neutral Platinum Methyl Complexes

The selective metal-catalyzed oxidation of alkanes to alcohols offers immense opportunities for saving energy and reducing waste in the petroleum and chemical manufacturing industries. Robust transition metal complexes with chelating nitrogen ligands show great promise as homogeneous catalysts for this reaction, but a practical system has yet to be identified. In this work a variety of neutral platinum methyl complexes with bidentate anionic N,N- and N,C-donor ligands were prepared. Ligand backbones included one, two, and three-atom bridges between the donor atoms. Redox properties of the new complexes were investigated using competition studies with I_2 and evaluating equilibrium constants between divalent methyl complexes and their tetravalent diiodides. The ease of oxidation was amidinate > β-diketiminate > iminopyrrolide. Studies of benzene C-H bond activation using iminopyrrolide platinum complexes were consistent with rate determining benzene association and revealed a novel geometric effect on the rate for iminopyrrolide ligands.