Formation and structural relationship of electroactive PtII–HgII polymetallic sulfide aggregates

Abstract

A series of {Pt₂HgS₂}, {Pt₂Hg₂S₂} and {Pt₄HgS₄} complexes, viz. [(Ph₃P)₄Pt₂(μ₃-S)₂HgCl₂] 2, [(Ph₃P)₄Pt₂(μ₃-S)₂Hg(PPh₃)]X₂ [X = Cl (3a) or PF₆ (3b)], [HgPt₄(PPh₃)₈(μ₃-S)₄]X₂ [X = PF₆, (4a) or ClO₄ (4b)], [Pt₂(Ph₃P)₄(μ₃-S)₂Hg₂(μ-Cl)₂Cl₂] 5, [(Ph₃P)₄Pt₂(μ₃-S)₂Hg₂(μ-Cl)₂(PPh₃)₂][PF₆]₂6 and [(Ph₃P)₄Pt₂(μ₃-S)₂Hg₂(NO₃)₂]X₂ [X = NO₃ (7a) or PF₆ (7b)] have been synthesized from [Pt₂(μ-S)₂(PPh₃)₄] 1 with the appropriate mercury(II) compounds through 1∶1, 1∶2 and 2∶1 Lewis acid–base additions. Formation of the major product is governed largely by the stoichiometric quantity of the substrates. Reaction intermediates can be isolated and characterized. Their conversions into the final products have been verified. Single-crystal X-ray crystallography on 2, 3b, 4b, 5 and 6 revealed a range of Pt^II/Hg^II metal sulfide cores with different nuclearities. V.T. ³¹P-{¹H} NMR study of 3b showed a rapid migration of the [Hg(PPh₃)] moiety between two sulfide sites in a {Pt₂HgS₂} core. Cyclic voltammetry was carried out on 2, 3b, 5 and 6. Complex 3b undergoes an approximately reversible one electron transfer oxidation with E_p,a = 1.10 V and E_p,c = 1.01 V.