Abstract
Direct- and alternating-current voltammetric investigations in CH2Cl2 of 17 variously substituted planar bis(dithio-β-diketonate) complexes [M(S2C3RHR′)2](M = Ni, Pd, or Pt and R,R′= But,CF3, Me, or Ph), including many new palladium and platinum complexes, confirm two reversible reductions in each case. The rapid rearrangement reported for [M(S2C3MeHMe)2] is largely suppressed in the other derivatives, apparently for steric rather than electronic reasons. The successive one-electron transfers are found to be ligand-centred in [M(S2C3RHR)2], as in the metal ‘dithienes’[M(S2C2R2)2], despite their difference in topology. An orderly and comparable dependence of reduction potentials on substituent influence (σ*R) is displayed by all such systems. The isostructural diketonates, [M(O2C3RHR′)2](M = Pd or Pt), show a parallel trend in first reduction potential and are systematically ca. 0.4 V more difficult to reduce than their dithio-analogues.

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