Mechanism and energetics of reductive elimination of ethane from some tetramethylplatinum(IV) complexes

Abstract

The new complexes cis-[PtMe₄L₂], L=MeNC or 2,6-Me₂C₆H₃NC, decompose cleanly in the solid state or in solution to give ethane and cis-[PtMe₂L₂]. Studies using differential scanning calorimetry give a value of [D with combining overline](PtMe)=133±kJ mol⁻¹for the mutually trans PtMe groups, and deuterium-labelling studies show that the reductive elimination step is intramolecular. Kinetic studies show that the reaction occures very largely after ligand dissociation and gives a value of k(PtCH₃)/k(PtCD₃)=1.30±0.04. It is suggested that an agostic interaction of one CH₃Pt group in the five-co-ordinate intermediate precedes the reductive elimination step and reasons for this proposal are advanced.