Antimonato polyoxovanadates with structure directing transition metal complexes: pseudopolymorphic {Ni(dien)2}3[V15Sb6O42(H2O)]·nH2O compounds and {Ni(dien)2}4[V16Sb4O42(H2O)]

Abstract

Three new poloxovanadates were synthesized under solvothermal conditions and were structurally characterized. The two compounds with composition {Ni(dien)₂}₃[V₁₅Sb₆O₄₂(H₂O)]·nH₂O (n = 12 and 8; dien = bis(2-aminoethyl)amine or diethylenetriamine) are pseudopolymorphs crystallizing in different space groups. The compounds were obtained by applying identical reaction slurries but using different reaction temperatures. Both compounds feature the [V₁₅Sb₆O₄₂(H₂O)]⁶⁻ anion which is the antimony analogue to the single molecule magnet [V₁₅As₆O₄₂(H₂O)]⁶⁻. Crystal data: 1 tetragonal space group P, a = 46.9378(3), c = 16.51300(10) Å and V = 36380.7(4) ų. 2 rhombohedral space groupR3c with a = 23.0517(4), c = 28.6216(5) Å and V = 13171.3(4) ų. In 1 several unusual short inter-cluster Sb⋯O contacts lead to the formation of three different super-clusters with composition V₆₀Sb₂₄O₁₆₈. The 12 unique {Ni(dien)₂}²⁺ complexes adopt all three possible configurations. In 2 the special arrangement of the {Ni(dien)₂}²⁺ complexes around the cluster anion prevents inter-cluster Sb⋯O contacts. The main structural motif of the third compound {Ni(dien)₂}₄[V₁₆Sb₄O₄₂(H₂O)] (3) is the [V₁₆Sb₄O₄₂(H₂O)]⁸⁻cluster anion consisting of two perpendicular eight-membered rings of VO₅ pyramids. Two additional VO₅ polyhedra are located on opposite sides. Crystal data: 3 triclinic space group P, a = 13.5159(4), b = 14.2497(5), c = 14.9419(4) Å, α = 98.322(2), β = 114.080(2), γ = 110.130(2)° and V = 2326.35(12) ų.