Semi-vacant Wells–Dawson anions. Synthesis of tri-tungsten-vacant derivatives and crystallographic studies of [αββα-(CuIIOH2)2(CuII)2(AsW15(OH2)3(OH)O52)2]12−

Abstract

The tri-tungsten-vacant polyoxometalate, [α-AsW₁₅(OH)₄O₅₂]¹³⁻, derived from the semi-vacant Wells–Dawson complex [α-AsW₁₈(OH)₄O₅₈]⁷⁻, reacts with the late-transition metal cations, Cu(II) or Zn(II), to form sandwich-type species; the X-ray crystal structure of [αββα-(Cu^IIOH₂)₂(Cu^II)₂(AsW₁₅(OH₂)₃(OH)O₅₂)₂]¹²⁻, prepared by the acidification of [αββα-(Cu^IIOH₂)₂(Cu^II)₂(AsW₁₅(OH)₄O₅₂)₂]¹⁸⁻, reveals that the missing heteroatoms are distal to the central Cu₄ unit and the vertices of the vacant tetrahedron are occupied by one OH⁻ and three OH₂ groups.