A comparison is made of the chemistry of platinum with the ligands 2-C5H4NCH2NH-C6H3-2-OH-5-R, when R = H (L) or NO2 (L1) in order to determine the effect of the nitro substituent in L1. With inorganic platinum(II) complexes, L1 acts as a bidentate ligand in [PtCl(SMe2)(κ2-N,N′-L1)]Cl or as a monodentate ligand in trans-[PtI2(SMe2)(κ 1-N-L1)] and, with a methylplatinum unit, it forms the zwitterionic complex [PtMe(SMe2)(κ 2-N,N′-L1-H)], which contains an uncoordinated phenoxide substituent. The reactive dimethylplatinum complex in acetone solution reacts with dioxygen to give the hydroxoplatinum(IV) complex [Pt(OH)Me2(κ 3-N,N′,O-L1-H)], in which the deprotonated L1 acts as a fac-tridentate ligand. The dimethylplatinum complex in CD2Cl2 solution actually exists as a mixture of the three possible fac-hydridodimethylplatinum(IV) isomers [PtHMe2(κ 3-N,N′,O-L1-H)], which slowly undergo reductive elimination of methane or, in the presence of excess D2O, a mixture of isotopomers CHnD4-n. It is proposed that the isomers [PtHMe2(κ 3-N,N′,O-L1-H)] interconvert via shortlived methane complex intermediates [PtMe(CH4)(κ 3-N,N′,O-L1-H)]. No similar reactivity is observed with the ligand L, thus demonstrating the remarkable effect of the nitro substituent.