INFLUENCE OF PROTONATION ON CRYSTAL PACKING AND THERMAL-BEHAVIOR OF TERT-BUTYLAMMONIUM DECAVANADATES

Two tert-butylammonium decavanadate(V) salts with the formulae [(CH3)( 3)CNH3](6)[V10O28]. 8H(2)O (1) and [(CH3)(3)CNH3](4)[H2V10O28] (2), ha ve been synthesized and their crystal structures have been determined by means of single-crystal X-ray diffraction. The crystal structure of compound 1 is stabilized by electrostatic forces and an extensive net work of hydrogen contacts involving anions, cations and water molecule s. The anions and cations of this compound are arranged inlayers perpe ndicular to the [010] direction following the sequence, cation-anion-c ation. In the crystal structure of compound (2), each dihydrogen decav anadate(V) anion is joined to three adjacent polyanions by means of O( 6)-H ... O(4) hydrogen contacts forming layers parallel to the plane ( (1) over bar 01) and the hydrophobic groups of the cations are dispose d in layers parallel to the anionic sheets. The thermal behaviour of b oth compounds has been studied. Compound 1 is an octahydrate and its t hermal decomposition begins at 70 degrees C with the loss of water of crystallization, while compound 2 is anhydrous and is consequently mor e stable, with decomposition starting at 200 degrees C. Copyright (C) 1996 Elsevier Science Ltd