[ASVV 12VV 2IVO40]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 12O38} unit with O(h) symmetry. It is formed from twelve VO6 octahedra sharing edges, which each also share a face with the central AsO6 octahedron. Two additional V = O groups cap the AsO6 octahedron. K7[As(v)V(v)12V(iv)2O40] . 12 H2O 1.