Phase transitions in metavanadates. Polymerization of tetrakis (tert-butylammonium)-cyclo-tetrametavanadate

The compound tetrakis(tert-butylammonium)-cyclo-tetra the first oxovanadate salt isolated from aqueous solution which contains a discrete unprotonated [V4O12](4-) anion, undergoes an irreversible, reconstructive, continuous, and heterogeneous phase transition in the solid state by means of a nucleation and growth mechanism. This transformation yields a polymeric metavanadate of tert-butylammonium and it has been followed by X-ray powder diffraction and FTIR techniques. The polymeric compound has also been isolated from aqueous solution and its crystal structure resolved by single-crystal X-ray diffraction methods, this compound crystallizes in the monoclinic space group P2(1), a = 10.397(2) Angstrom, b = 5.873(1) Angstrom, c = 13.879(4) Angstrom, beta = 111.02(3)degrees, V = 791.1(3) Angstrom(3), Z = 4, and R = 0.026 for 1926 observed reflections with I greater than or equal to 3 sigma(I). Comparison of the polymeric and cyclic metavanadate structures reveals several structural similarities such as V ... V contacts and V-O-V angles. A possible transformation mechanism has been suggested on the basis of these structural analogies.