Disorder in Crystalline Organosilicon Compounds Si2R6:  A Solid-State NMR Study

Variable-temperature 13C and 29Si CP/MAS NMR studies of the solid-state dynamic properties of compounds Si2R6 (R = t Bu, 1; R = SiMe3, 2) are reported. Both structural phase transitions and internal molecular reorientational processes are detected by high-resolution solid-state NMR. Internal reorientational processes in 1 and 2 are not suppressed by massive steric intramolecular crowding. Quantification of the internal t Bu reorientation characteristics in 1, as determined experimentally by NMR in conjunction with spectral line shape simulations, is in good agreement with the results of molecular dynamics simulations based on the single-crystal structure of 1.