The novel sandwich-type heteropolyoxotungstates [M2Bi2(β-B-MW9O34)2]14− (M = CoII, ZnII): β-type dimeric heteropolyanions with a transition metal as the central heteroatom and BiIII and M as linking atoms

Abstract

Two new sandwich-type heteropolyoxometalates, Na₁₄[Co₂Bi₂(β-B-CoW₉O₃₄)₂]·48H₂O (1) and Na₁₄[β-B-Zn₂Bi₂(ZnW₉O₃₄)₂]·51H₂O (2), have been synthesized at pH = 7.5–8 and characterized by elemental analysis, IR, UV-vis, TG-DSC and electrochemistry. Structural analysis indicates that both polyanions, M₂Bi₂(β-B-MW₉O₃₄)₂]¹⁴⁻ (M = Co^II and Zn^II), are isomorphic and consist of two unprecedented [β-B-MW₉O₃₄]¹²⁻ subunits linked by two M^II and two Bi^III which are coplanar. The polyanions are also the first examples of dimeric heteropolyanions with Bi^III only as the second (linking) heteroatom and the transition metals (Co^II or Zn^II) as the first and second heteroatoms as well. The lower absorption of ν(W–O_d) (915 cm⁻¹) in the IR is a simple and feasible judgment of sandwich-type polyanions with a transition metal ion as a central heteroatom.