The rôle of d functions in the Si—N bond

(p $\rightarrow $ d) $\pi $-bonding to silicon in SiH$_{3}$NCO, SiH$_{3}$N$_{3}$ and (SiH$_{3}$)$_{3}$N has been investigated by examining the stereochemistry, dipole moments and low-energy photoelectron spectra of these molecules and their carbon analogues using ab initio and semi-empirical molecular orbital theory. It is concluded that although (p $\rightarrow $ d) $\pi $-bonding may play an important part in the Si-N bond it does not directly control the stereochemistry of the silicon pseudohalides.