Dimethyl(hydrido)platinum(IV) chemistry related to methane activation: the effect of a tetradentate ligand

The complex [PtMe2(TPMA)] (1), TPMA=tris(2-pyridylmethyl)amine, contains bidentate TPMA with two free pyridyl groups. It reacts with HX (X=CF3CO2, CF3SO3, BF4) at room temperature to yield [PtHMe2(TPMA)][X], which exists as an equilibrium mixture of two isomeric forms, each containing fac-tridentate TPMA. The major product has the hydride trans to a pyridyl group, but an equilibrium exists with the isomer in which the hydride is trans to amine. These cationic methyl(hydrido)platinum(IV) complexes are stable at room temperature for several hours, but undergo slow reductive elimination of CH4 to yield [PtMe(TPMA)][X], in which TPMA is mer-tridentate. The reaction of 1 with CF3SO3D in CD3OD gives only CH3D, with no deuterium incorporation into the remaining methylplatinum group, and with MeI it yields [PtMe3(TPMA)][I].