Carbon–Hydrogen versus Nitrogen–Oxygen Bond Activation in Reactions of N‑Oxide Derivatives of 2,2′-Bipyridine and 1,10-Phenanthroline with a Dimethylplatinum(II) Complex

The reactions of the potential oxygen atom donor ligands 1,10-phenanthroline N-oxide (phenO) and 2,2′-bipyridine N-oxide (bipyO) with the dimethylplatinum­(II) complex [Pt2Me4(μ-SMe2)2] are reported. The reaction with the more rigid ligand phenO gave [PtMe2(κ2N,O-phenO)], which underwent oxidative addition with 4-t-Bu-C6H4CH2Br to give the platinum­(IV) complex [PtBrMe2(CH2C6H4-4-t-Bu)­(phenO)]. The complex [PtMe2(phenO)] reacted with methanol in air to give [Pt­(OH)­(OMe)­Me2(phenO)], but under an inert atmosphere it gave [Pt­(OH)­(OMe)­Me2(phen)], in a reaction involving N–O bond activation. In contrast, the reaction of [Pt2Me4(μ-SMe2)2] with bipyO occurred by C–H bond activation to give methane and [PtMe­(κ2N,C-C5H4N-C5H3NO)­(SMe2)], which underwent ligand substitution with pyridine, triphenylphosphine, or bis­(diphenylphosphino)­methane (dppm) to give [PtMe­(κ2N,C-C5H4N-C5H3NO)­(NC5H5)], [PtMe­(κ2N,C-C5H4N-C5H3NO)­(PPh3)], or the binuclear [{PtMe­(κ2N,C-C5H4N-C5H3NO)}2(μ-dppm)], respectively. With bis­(diphenylphosphino)­ethane (dppe), ligand substitution gave [PtMe­(κ1C-C5H4N-C5H3NO)­(dppe)], which contains a monodentate metalated bipyO ligand. The mechanisms of the key reactions are discussed.