Synthesis and structural characterization of tube-type tetradecavanadates

By the reaction of ammonium perchlorate with anion-incorporated bowl-type dodecavanadates, viz. [V₁₂O₃₂(X)]^5- [X = N₃^- (1), OCN^- and NO₃^-], tube-type tetradecavanadates, viz. (NH₄)₇[V₁₄O₃₈(X)] [X = N₃^- (2), OCN^- (3) and NO₃^- (4)] were synthesized. The crystal structures of penta(tetraethylammonium) azidododecavanadate nitromethane monosolvate, (C₈H₂₀N)₅[V₁₂O₃₂(N₃)]·CH₃NO₂, 1, heptaammonium azidotetradecavanadate dimethyl sulfoxide hexasolvate, (NH₄)₇[V₁₄O₃₈(N₃)]·6C₂H₆OS, 2, heptaammonium cyanatotetradecavanadate dimethyl sulfoxide hexasolvate, (NH₄)₇[V₁₄O₃₈(OCN)]·6C₂H₆OS, 3, and heptaammonium nitratotetradecavanadate dimethyl sulfoxide hexasolvate, (NH₄)₇[V₁₄O₃₈(NO₃)]·6C₂H₆OS, 4, were determined. The tube consists of two layers of V₇ rings with a guest anion at the centre. The distances between the incorporated anions and the nearest V atoms are 3.058 (3), 3.039 (6) and 2.811 (9) Å for 2, 3 and 4, respectively, showing that the incorporated anions are stabilized via noncovalent interactions. Two ammonium cations cap both ends of the tube to stabilize the structures via hydrogen-bonding interactions. Linear OCN^- and N₃^- anions sit on the twofold rotation axes of the tube frameworks and the triangular plane of the NO₃^- anion deviates from the equatorial plane of the tube by ca 30°.