Solid State Dynamic Properties of Tetrakis(trimethylsilyl)methane: High-Resolution Solid State 13C and 29Si NMR Investigations
Abstract
The dynamic properties of solid tetrakis(trimethylsilyl)methane (C(Si(CH 3) 3) 4; TTMSM) have been determined using high-resolution solid state 13C and 29Si NMR spectroscopy. TTMSM is known to undergo a phase transition from a high-temperature "rotator" phase, in which there is isotropic reorientational motion of the molecule within the solid, to a low-temperature phase in which the molecular motion becomes anisotropic. In this low-temperature phase, one Si Me 3 group of the TTMSM molecule becomes inequivalent from the other three Si Me 3 groups and the molecules undergo two different types of dynamic process. These are classified as (1) exchange between the crystallographically unique Si Me 3 group and an Si Me 3 group within the set of three equivalent Si Me 3 groups, and (2) hindered rotation of each Si Me 3 group about the relevant C[central]-Si bond. The energy barriers for these dynamic processes are discussed, and the dynamic behavior of TTMSM is compared with that reported previously for solid tetrakis(trimethylsilyl)silane. The 13CNMR results strongly suggest that the molecular symmetry of the TTMSM molecule in the low-temperature phase is C 3.
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- June 1994
- DOI:
- 10.1006/jssc.1994.1174
- Bibcode:
- 1994JSSCh.110..314A