Protonolysis of dimethylplatinum(II) complexes: Primary attack at metal or ligand

The complexes [PtMe2(DMEP)], 1, and [PtMe2(DMPP)], 2 [DMEP, DMPP = Me2N(CH2)(n)N=CH-2-C5H4N, n = 2, 3, respectively], contain ligands that chelate to platinum through the imine and pyridyl groups, with the tertiary amine group not coordinated. Methyl iodide reacted with complex 1 to give [PtIMe3(DMEP)] but reacted with 2 to give a mixture of [PtIMe3(DMPP)] and [PtMe3(DMPP)]I, indicating the greater ability of DMPP to act as a fac-tridentate ligand. Complex 2 reacted with MeO3SCF3 to form [PtMe3(DMPP)][CF3SO3] only. The primary reaction of 1 and 2 with HX (X = Cl, O2CCF3, or O3SCF3) occurred by protonation of the pendant amine, while with excess acid, a methylplatinum bond trans to imine was cleaved selectively. Two products of protonolysis, namely [PtMe(DMEP)][O3SCF3], containing mer-tridentate DMEP, and [PtMe(O2CCF3)(DMEPH][O2CCF3], with a protonated bidentate DMEP ligand, have been characterized by structure determinations, and the reaction pathways have been deduced by monitoring the reactions by H-1 NMR at varying temperature. In the reaction of 2 with HCl, an intermediate hydridoplatinum(IV) complex [PtHClMe2(DMPPH)][Cl] was detected and determined to be stable up to -30 degrees C, when it decomposed to give methane and [PtClMe(DMPPH][Cl].