Structure and dynamics of solid tris(trimethylsilyl)amine by deuterium nuclear magnetic resonance spectroscopy

Abstract

Deuterium NMR spectra for solid [²H₉] tris (trimethylsilyl) amine were recorded at 77 K and in the region 114–353 K. At 77 K there is only fast rotation of the methyl groups. Between 122 and 171 K rotation of the trimethylsilyl groups and of the entire molecule (about its C₃ axis) affect the deuterium NMR line shape. Above 180 K both motions are fast (> 10⁵ Hz). There is a phase transition at 227 ± 2 K. Above 227 K the molecule undergoes a fast precessional motion of increasing effective amplitude until the melting point (343 K). The only dynamic model capable of explaining the spectra at temperatures above 180 K requires the three N–Si bonds to be coplanar.