Consistent with the relative p-acceptor capabilities (Si i Pr3 < Si t BuPh2 < SiPh3), the N-Si bond lengths decrease slightly (and To gain additional insight, the M-N bonds were analysed using the ETS-NOCV method, to identify the key contributions to the orbital interaction term DEorb (Table ; ESI). Cationic [(NON)M] + and dianionic [NR] 2-fragments were chosen as reference states. Within this scheme, the M-N bond is comprised of both s and p interactions, with the latter split into a pair of mutually orthogonal components. For the aluminium imides, s interactions account for ca. 52-57% of DEorb, and p interactions ca. 25-30%, while for