Formation of Group 14 and 15 heteroatom derivatives of trinuclear [M3Se4(H2O)9]4+ (M = Mo, W) and the decreased reactivity of [W3S4(H2O)9]4+

Abstract

Group 14 and 15 elements (M′ = Pb, As, Sb, Bi), which are known to form corner-shared double cube derivatives [Mo₆M′S₈(H₂O)₁₈]⁸⁺ of [Mo₃S₄(H₂O)₉]⁴⁺, are here shown to react with [M₃Se₄(H₂O)₉]⁴⁺ (M = Mo, W). Using similar procedures, no corresponding derivatives of [W₃S₄(H₂O)₉]⁴⁺ are obtained. ICP-AES metal analyses on the [M₃Se₄(H₂O)₉]⁴⁺ products, together with stoichiometries for oxidation with the Co^III oxidant [Co(dipic)₂]⁻, are consistent with corner-shared double cube formulae [M₆M′Se₈(H₂O)₁₈]⁸⁺. UV-Vis spectra are reported as part of the characterisation, and observations are made on the reactivity of the cubes with O₂. The X-ray crystal structures of [Mo₃Se₄(H₂O)₉](pts)₄·10H₂O, [W₃Se₄(H₂O)₉](pts)₄·12H₂O and one of the key products [Mo₆AsSe₈(H₂O)₁₈] (pts)₈·8H₂O have been determined (pts⁻ = p-toluenesulfonate). Whereas differences in reactivity of [Mo₃Se₄(H₂O)₉]⁴⁺ and [W₃Se₄(H₂O)₉]⁴⁺ are small, the differences for [Mo₃S₄(H₂O)₉]⁴⁺ and [W₃S₄(H₂O)₉]⁴⁺ are much more marked. In the context of heteroatom incorporation the incomplete cube [W₃S₄(H₂O)₉]⁴⁺ is by far the least reactive of the four trinuclear clusters.