Thermal and methyllithium-assisted cyclometallation reactions of η3-allyl(methyl)(tertiary phosphine or phosphite)platinum(II) complexes

Abstract

The complexes [Pt(η³-C₃H₅)Me(L)][L = P(C₆H₄Me-o)₃, PPh₂(CH₂Ph), PPr₃ and P(OPh)₃] have been prepared and characterized by ¹H and ¹³C NMR spectroscopy. Four of these complexes decompose in boiling toluene to give the cyclometallated complexes [Pt(η³-C₃H₅)(P–C)](P–C = cyclometallated phosphine or phosphite), which have also been characterized spectroscopically. The complex [[graphic omitted](C₆H₄Me-o)₂}] exists as a novel pair of conformers in solution. Addition of an equivalent of methyllithium to a solution of [Pt(η³-C₃H₅)Me{P(C₆H₄Me-o)₃}] in toluene promotes cyclometallation of the phosphine ligand, giving the cyclometallated product without heating, while using tetrahydrofuran does not give a cyclometallated product. A tentative mechanism of the methyllithium-assisted cyclometallation reaction is proposed based on the product analysis.