Activation of a C-H bond in a pyridine ring. Reaction of 6-substituted 2,2 '-bipyridines with methyl and phenyl platinum(II) derivatives: N ',C(3)-"rollover" cyclometalation

The reaction of the electron-rich derivatives cis-[Pt(R)(2)(DMSO)(2)] (R = Me, Ph) with a series of 6-substituted-2,2'-bipyridines, HL, occurs with loss of methane or benzene, respectively, to yield cyclometalated platinum(II) species [Pt(R)(L)(DMSO)] where L is an anionic ligand N',C(3) coordinated. The unusual C-H activation entails a consecutive reaction process through a detectable intermediate. The reaction is peculiar of 6-substituted ligands: for comparison no reaction occurs with 6,6'-Me2-2,2'-bipy and an adduct, [Pt(R)(2)(HL)], is obtained with 5-Me-2,2'-bipy.