Four new lead(II) thiolate cluster complexes -: Unexpected products of a conventional synthesis

The reaction of Pb(OOCCH3)(2) center dot 3H(2)O with 2.1 equiv. of HS-2,6-(CH3)(2)C6H3 in ethanol/water is expected to give [Pb{S-2,6-(CH3)(2)C6H3}(2)]. However, we obtained an orange powder whose elemental analysis disagrees with that of the expected product and indicates small amounts of oxygen. Layering of concentrated solutions of this orange powder in dry THF with pentane under nitrogen results in the formation of a mixture of three identifiable crystalline compounds, namely [Pb-10{S-2,6-(CH3)(2)C6H3}(20)], [Pb6S{S-2,6-(CH3)(2)C6H3)(10)(C4H8O)(4)] and [Pb8O2{S-2,6-(CH3)(2)C6H3}(12)]. In contrast, fractional crystallization from dilute solutions initially yielded only yellow crystals of [Pb14O6{S-2,6-(CH3)(2)C6H3}(16)]. Further concentration of the supernatant solution yielded, upon layering with pentane, [Pb6S{S-2,6-(CH3)(2)C6H3)(10)(C4H8O)(4)] and [Pb-10(S-2,6-(CH3)(2)C6H3}(20)], which are almost completely separable by controlling the duration of the crystallization step and the amount of condensed pentane. Recrystallization of the crude orange powder under aerobic conditions produces pure [Pb14O6(S-2,6-(CH3)(2)C6H3}(16)] with a yield five times higher than that under nitrogen. This shows that it is sensitive to oxidation by oxygen in solution. The structures of all four complexes have been determined by single-crystal X-ray analysis. The net formed by the six oxygen and twelve lead atoms in the center of [Pb-14 O-6{S-2,6-(CH3)(2)C6H3}(16)] resembles a small piece of a layer of the solid-state structure of red PbO. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).