SYNTHESIS, CRYSTAL-STRUCTURE AND THERMAL-PROPERTIES OF (NH4)(2)CO2V10O28-CENTER-DOT-16H(2)O

Powder and single-crystals of a new compound have been obtained by a ' chimie douce' method. The crystal structure determined on single cryst al allows to assign to this compound the structural formula [Co(H2O)(6 )](2)[NH4](2)V10O28.4H(2)O. It crystallizes in the triclinic system, s pace group P-1 with a = 8.836(3) Angstrom, b = 10.865(6) Angstrom, c = 11.052(5) Angstrom, alpha = 65.18(4)degrees, beta = 74.12(4)degrees, gamma = 71.57(3)degrees; Z = 1; V = 901.3(8) Angstrom two NH4, and fou r H2O groups by hydrogen bonds. The thermal properties are described a nd discussed in relation with other decavanadates. The loss of water m olecules and ammonia occurs in several steps, and the structure collap ses around 380 degrees C to give a mixture of V2O5 and alpha-Co(VO3)(2 ).