Electrochemical and theoretical study of the redox properties of transition metal complexes with {Pt2S2} cores

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Abstract
The oxidation processes undergone by the {Pt2(μ-S)2} core in [Pt2(P∩P)2(μ-S)2] (P∩P = Ph2P(CH2)nPPh2, n = 2,3) complexes have been analysed on the basis of electrochemical measurements. The experimental results are indicative of two consecutive monoelectronic oxidations after which the {Pt2(μ-S)2} core evolves into {Pt2(μ-S2)}2+, containing a bridging disulfide ligand. However, the instability of the monoxidised [Pt2(P∩P)2(μ-S)2]+ species formed initially, which converts into [Pt3(P∩P)3(μ-S)2]2+, hampered the synthesis and characterisation of the mono and dioxidised species. These drawbacks have been surpassed by means of DFT calculations which have also allowed the elucidation of the structural features of the species obtained from the oxidation of [Pt2(P∩P)2(μ-S)2] compounds. The calculated redox potentials corresponding to the oxidation processes are consistent with the experimental data obtained. In addition, calculations on the thermodynamics of possible processes following the degradation of [Pt2(P∩P)2(μ-S)2]+ are fully consistent with the concomitant formation of monometallic [Pt(P∩P)S2)] and trimetallic [Pt3(P∩P)3(μ-S)2]2+ compounds. Extension of the theoretical study on the {Pt2Te2} core and comparisons with the results obtained for {Pt2S2} have given a more general picture of the behaviour of {Pt2X2} (X = chalcogenide) cores subject to oxidation processes.