The redox chemistry of mononuclear and dinuclear gold(I) phosphine arylthiolate complexes
was recently investigated by using electrochemical, chemical, and photochemical techniques. We
now report the redox chemistry of dinuclear gold(I) phosphine complexes containing aliphatic
dithiolate ligands. These molecules differ from previously studied gold(I) phosphine thiolate
complexes in that they are cyclic and contain aliphatic thiolates. Cyclic voltammetry experiments of
Au2(LL)(pdt) [pdt = propanedithiol; LL = 1,2-bis(diphenylphosphino)-ethane (dppe),
1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb),
1,5-bis(diphenylphosphino)pentane (dpppn)] in 0.1 M TBAH/CH3CN or CH2Cl2 solutions at 50 to
500 mV/sec using glassy carbon or platinum electrodes, show two irreversible anodic processes at
ca. +0.6 and +1.1 V (vs. SCE). Bulk electrolyses at +0.9 V and +1.4 V result in n values of 0.95
and 3.7, respectively. Chemical oxidation of Au2(dppp)(pdt) using one equivalent of Br2
(2 oxidizing equivalents) yields 1,2-dithiolane and Au2(dppp)Br2. The reactivity seen upon mild
oxidation ≤ +1.0 V is consistent with formal oxidation of a thiolate ligand, followed by a fast
chemical reaction that results in cleavage of a second gold-sulfur bond. Oxidation at higher
potentials (≥ +1.3 V) is consistent with oxidation of gold(I) to gold(III). Structural and
electrochemical differences between gold(I) aromatic and aliphatic thiolate oxidation processes are
discussed.
