A Hexanuclear Cobalt(II) Cluster Incorporated in a Banana‐Shaped Tungstovanadate: [(Co(OH2)Co2VW9O34)2(VW6O26)]17–

Abstract

AbstractThe hexanuclear cobalt‐containing tungstovanadate complex, Na17[(Co(OH2)Co2VW9O34)2(VW6O26)]·31H2O (1) has been synthesized through reaction of cobalt nitrate, sodium tungstate, and V2O5 in acetate buffer solution. The title compound has been characterized by X‐ray crystallography, elemental analysis, FTIR, UV/Vis, and 51V NMR spectroscopy and by cyclic voltammetry. Complex 1 crystallizes in the monoclinic space group P21/c (a = 15.706(3) Å, b = 21.973(5) Å, c = 35.080(8) Å, α = 90°, β = 97.420(3)°, γ = 90°; V = 12005(5) Å3; Z = 4; based on 192337 independent reflections), which consists of two tri‐CoII substituted B‐α‐[(Co(OH2)Co2VW9O39)] Keggin units bridged by one unique [VW6O16] fragment leading to a banana‐shaped structure with idealized C2ν symmetry. Stability studies show that polyoxoanion 1 ultimately transforms into the tetracobalt‐containing sandwich‐type polyoxoanion, 2, as confirmed by 51V NMR and X‐ray crystallographic analyses. Polyoxoanion 1 shows catalytic activity for the H2O2‐based epoxidation of 1‐hexene and cyclohexene in 1,2‐dichloroethane solvent.