Wide-line NMR study of silicon-nitrogen compounds

Abstract

(Me 3Si) 2NSi(Me) N Cl 3− N ( N = 0, 1, 2, 2, 3), (Me 3Si) 2NH, [(Me) 2ClSi] 2NH, and [(Me) 2ClSiNSiMe 2] 2 were studied by wide line NMR over the temperature range 77–300°K. The experimental line widths and second moments were calculated from the NMR absorption spectra. Theoretical line shapes and second moments were calculated for various motions to determine the actual inter-molecular and intra-molecular motions present. In particular, rotation of Me N Cl 3− N Si ( N = 1, 2, 3) groups about the SiN bond was studied. Powder X-rays were taken for the five crystalline compounds over the same temperature range to study possible phase changes. Activation energies were calculated for the various motions found to be present, and an attempt was made to correlate the barriers to rotation of the Me N Cl 3− N Si- groups about their SiN bond with changes in the symmetry of dπ- pπ bonding about the SiN bond. However, it was not possible to show any definite correlation and the differences in the barriers were best explained by differences in the intermolecular barriers.