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°.