NMR determination of dynamic parameters of CH3 groups in P(CH3)(4)SbCl6

The longitudinal relaxation time T-1 and the second moment M-2 of H-1 NMR l ine in a wide temperature range have been measured for P(CH3)(4)SbCl6. It w as found that two different methyl groups in each tetramethylphosphonium ca tion perform two different rates of C-3 motions. The reduction of the proto n second moment M-2 just below the temperature of the phase transition T-c2 = 350 K may suggest that the isotropic tumbling of the whole cation [P(CH3 )(4)](+) is involved in the structural change of the crystal lattice induce d by the movements of the [SbCl6](-) anion. (C) 1999 Elsevier Science B.V. All rights reserved. reserved.