The reaction of Ph2P(O)py-2 (HL) with methyl- and dimethylplatinum(II) derivatives afforded a series of six-membered C,N-cyclometallated species, [PtX(L')(L)] (X=halide or Me L' = neutral ligand, e.g, SMe2, SOMe2, CO, PAr3) arising from activation of one C(sp(2))-H bond of a phenyl substituent, The metallation entailed elimination of methane and caused the phosphorus atom to become chiral. The series includes the complex [Pt(Me)(CO)(L)] where the platinum atom is bonded to three different carbon atoms (C-sp(3), C-sp(2), C-sp), From the neutral species cationic derivatives [Pt(L')(L")(L)](+) (L' = SMe2,, L" = CH3CN; L'-L" = dppe; L' = SMe2 or SOMe2, L" = H2O) could be obtained, The new complexes were isolated and fully characterised by elemental analyses and spectroscopic techniques (IR, NMR, FAB-MS). The solid-state structures of [PtCl(SMe2)(L)], [PtCl(CO)(L)], [Pt(Me)(SOMe2)(L)], and [Pt(SMe2)(H2O)(L)][BF4] were determined by single-crystal X-ray diffraction.