Chemistry of platinum(IV), platinum(II) and palladium(II) cyclometallates of benzylthio- or benzosulphinyl-substituted azobenzenes

Abstract

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)Ci]. 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(MeL(su1)Cl] have been determined by an X-ray diffraction study. The S(O)CH₂Ph group is coordinated via the sulphur atom.