A Hexanuclear Cobalt(II) Cluster Incorporated in a Banana‐Shaped Tungstovanadate: [(Co(OH 2 )Co 2 VW 9 O 34 ) 2 (VW 6 O 26 )] 17–

The hexanuclear cobalt‐containing tungstovanadate complex, Na 17 [(Co(OH 2 )Co 2 VW 9 O 34 ) 2 (VW 6 O 26 )] · 31H 2 O ( 1 ) has been synthesized through reaction of cobalt nitrate, sodium tungstate, and V 2 O 5 in acetate buffer solution. The title compound has been characterized by X‐ray crystallography, elemental analysis, FTIR, UV/Vis, and 51 V NMR spectroscopy and by cyclic voltammetry. Complex 1 crystallizes in the monoclinic space group P 2 1 / 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) Å 3 ; Z = 4; based on 192337 independent reflections), which consists of two tri‐Co II substituted B‐α‐[(Co(OH 2 )Co 2 VW 9 O 39 )] Keggin units bridged by one unique [VW 6 O 16 ] fragment leading to a banana‐shaped structure with idealized C 2 ν symmetry. Stability studies show that polyoxoanion 1 ultimately transforms into the tetracobalt‐containing sandwich‐type polyoxoanion, 2 , as confirmed by 51 V NMR and X‐ray crystallographic analyses. Polyoxoanion 1 shows catalytic activity for the H 2 O 2 ‐based epoxidation of 1‐hexene and cyclohexene in 1,2‐dichloroethane solvent.