[AS V V 12 V V 2 IV O 40 ] 7⊖ , a Topologically Interesting, Mixed Valence Cluster as Model for Vanadium Minerals Formed by Weathering

A surprisingly low V IV /V V ratio is present in the cluster anion of 1 . Its structure (picture right; V black, As shaded, O open circles) may be described as a {AsV 12 O 38 } unit with O h symmetry. It is formed from twelve VO 6 octahedra sharing edges, which each also share a face with the central AsO 6 octahedron. Two additional VO groups cap the AsO 6 octahedron.\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$${\rm K_7[As^V{V_{12}^{V}}{V_2^{IV}}O_{40}]}\cdot 12\,{\rm H_2O}\quad {\bf 1}.$$\end{document}