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‘-Me 2 -2,2‘-bipy and an adduct, [Pt(R) 2 (HL)], is obtained with 5-Me-2,2‘-bipy.