The heterometallic corner-shared double-cuboidal cluster [Mo6PbS8(H2O)18]8+, with the lead atom common to both cubes, has been prepared for the first time by the reaction of [Mo3S4(H2O)9]4+ with lead shot, which requires up to 1 h to reach completion, and by addition of a solution mix of [Mo3S4(H2O)9]4+ and PbII to an excess of BH4–, when reaction is rapid. The air-sensitive blue-green product has UV/VIS absorbance bands at 387 and 757 nm in 2.0 M HClO4. Inductively coupled plasma atomic emission spectroscopy confirmed the Mo : Pb : S ratio as 6 : 1 : 8. It was eluted from a cation-exchange column with 4 M Hpts (toluene-p-sulfonic acid), but not 2 M Hpts (or 4 M HClO4), consistent with a high charge, confirmed as 8 + from the 2 : 1 stoichiometries for the oxidation reactions with e.g.[Co(dipic)2]–(dipic = pyridine-2,6-dicarboxylate) or [Fe(H2O)6]3+, which yield [Mo3S4(H2O)9]4+. Kinetic studies on the oxidations with [Co(dipic)2]– and [Fe(H2O)6]3+ were also carried out as part of an overall appraisal of the reactivity of the heterometallic clusters.
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Saysell et al. (1996) studied this question.