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

摘要

The crystal structure of 1,3,5-trimethylpyridinium hexachlorometallates [(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 the 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 diffraction. 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 tellurate. Another cationic motion, with an activation energy of about 20 kJ mol(-1), was observed above 380 K for both salts. This is attributable to the pseudo-C-3 reorientation around the axis perpendicular to the pyridinium ring. The cationic motions and the crystal structure are discussed from the point of view of the hydrogen bonding. (C) 1998 Elsevier Science B.V. [References: 19]