CATIONIC MOTIONS AND CRYSTAL-STRUCTURES OF 1,3,5-TRIMETHYLPYRIDINIUM HEXACHLOROMETALLATES [(CH3)(2)C5H3N(CH3)](2)MCL6 (M IS SN AND TE) STUDIED BY H-1-NMR AND X-RAY-DIFFRACTION

The crystal structure of 1,3,5-trimethylpyridinium hexachlorometallate s [(CH3)(2)C5H3N(CH3)](2)MCl6 (M is Sn and Te) were determined at 298 K and found to be orthorhombic Pnnm (No. 58) and Z = 2, a = 8.996(2), b = 11.330(2), c = 11.596(2) Angstrom, V = 1182.0(7) Angstrom(3) for t he stannate, and a = 9.072(4), b = 11.399(5), c = 11.63(2) Angstrom, V = 1203(3) Angstrom(3) for the tellurate, by single crystal X-ray diff raction. No phase transition was detected by DTA from 80 to 573 K. The cationic motions were studied by H-1 NMR and the C-3 reorientation of the CH3 groups was observed below 273 K, having an activation energy of 3.1 kJ mol(-1) for the stannate and 3.7 kJ mol(-1) for the tellurat e. Another cationic motion, with an activation energy of about 20 kJ m ol(-1), was observed above 380 K for both salts. This is attributable to the pseudo-C-3 reorientation around the axis perpendicular to the p yridinium ring. The cationic motions and the crystal structure are dis cussed from the point of view of the hydrogen bonding. (C) 1998 Elsevi er Science B.V.