CHEMISTRY OF PLATINUM(IV), PLATINUM(II) AND PALLADIUM(II) CYCLOMETALLATES OF BENZYLTHIO-SUBSTITUTED OR BENZOSULPHINYL-SUBSTITUTED AZOBENZENES

Cyclometallated platinum(IV) complexes of the type [Pt(RL)Cl3] incorporating azobenzene (R = H) or 4-methylazobenzene (R = Me) with an SCH2Ph (L = L1) or an S(O)CH2Ph (L = L2) substituent in an ortho position are described. These were obtained by oxidative addition of chlorine to [Pt(II)(RL)Cl]. Analogous palladium(II) complexes, however, gave chloro-substituted azobenzenes upon reaction with chlorine. The platinum(IV) complexes show an irreversible cyclic voltammetric metal reduction peak near -0.3 V vs SCE. Constant potential coulometric reduction at -0.5 V or chemical reduction by hydrazine hydrate regenerated [Pt(II)(RL)Cl]. The structures of [Pt(HL1)Cl3], [Pt(MeL2)Cl] and [Pd(MeL1)Cl] have been determined by an X-ray diffraction study. The S(O)CH2Ph group is coordinated via the sulphur atom.