Given the (coordination-) polymeric nature of K[1a], we hypothesized that employing less symmetric silyl substituents or those without a SiPhn moiety might result in less strongly aggregated (and by implication more soluble) imide derivatives. As such, aluminium imides bearing Si t BuPh2 or Si i Pr3 substituents were targeted. The reaction of K2[(NON)Al]2 with t BuPh2SiN3 can be shown by in situ 1 H NMR monitoring to lead to clean conversion to a single product. Uptake of only one Si t BuPh2 unit per NON ligand backbone is indicated by integration of the signals at dH = 1.28 ( t Bu) and 7.95 ppm (ortho CH) associated with the silyl group with respect to the NON backbone signals at dH = 6.38 and 6.73 ppm. Gratifyingly, the silylimide product in this case is soluble in aromatic solvents, and crystals suitable for X-ray diffraction (and elemental microanalysis) could be obtained from benzene solution, confirming the formation of K[(NON)Al{N(Si t BuPh2)}], K[1b] (Scheme 2 and Figure ). In the solid state, K[1b] also adopts a polymeric structure analogous to that of K[1a]. The Al-N and N-Si distances (1.7351(15)/1.7304(15) and 1.6576(14)/1.6584(15) Å, for the two molecules in the asymmetric unit) are also similar to those of K[1a] (1.740(6)/1.730(6) and 1.657(6)/1.644(5) Å). The Al-N-Si angle is somewhat wider for K[1b] than for K[1a] (138.73(9)/138.99(9)° vs 131.0(3)/130.9(3)°), presumably on steric grounds, although both are narrower than the corresponding Al-N-C angle observed for Dipp-substituted imide K2[VII]2 (146.43(17)°). Interestingly, the O-Al-N-Si dihedral angles (56.44(16), 55.00(16)°) measured for K[1b] differ significantly from those measured for either K[1a] or K2[VII]2 (37.6(5)/41.9(5) and 75.9(4)°), presumably reflecting not only the differing steric profiles of the imide substituents, but also a degree of angular flexibility consistent with the minor role of Al=N p bonding. Potassium aluminyl compound K2[(NON)Al]2 was also reacted with i Pr3SiN3 to afford K[(NON)Al{N(Si i Pr3)}], K[1c]. In this case, although the reaction proceeds quantitatively (as judged by in situ 1 H NMR monitoring), attempts to isolate the product at room temperature invariably lead to decomposition, and K[1c] was therefore prepared and used in situ for onward reactivity studies. The formulation of K[1c] as K[(NON)Al{N(Si i Pr3)}] is implied by its onward reactivity (see below). Finally, with a view to expanding the scope of heteroatom derived N-substituents, K2[(NON)Al]2 was reacted with {(HCNDipp)2B}N3 targeting the formation of an aluminium borylimide. While this proves to be feasible, the compound so generated K[(NON)Al{NB(NDippCH)2}], (K[1d]) is also extremely labile, decomposing rapidly in solution, and (more slowly) in the solid state. An in situ acquired 1 H NMR spectrum, features signals consistent with a symmetric NON ligand environment (e.g. two 2H doublets for the xanthene backbone at dH = 6.14 and 6.57 ppm), and an unsymmetrical diazabutadiene environment (e.g. two mutually coupled 1H NCH backbone signals at dH = 5.96 and 6.28 ppm). The 11 B NMR signal shifts from dB = 19.5 ppm for the parent azide compound to dB = 24.8 ppm. K[1d] is highly unstable, decomposing very rapidly in solution; nonetheless, the molecular structure of K[1d] could be determined from single crystals grown rapidly from supersaturated solution (minimal solvent) at 283 K and immediately harvested/manually separated for data collection (Scheme 3). In the solid state K[1d] adopts a monomeric structure (in contrast to K[1a] and K[1b]), with the tendency to aggregate via bridging K + /arene interactions being frustrated by encapsulation of the potassium counterion between the bulky boryl and aluminylderived Dipp groups of the same imide complex. Within the [(NON)Al{NB(NDippCH)2}] -unit, the Al-N distance (1.739(2) Å), Al-N-B angle (136.6(2)°), and O-Al-N-B torsion (61.8(3)°) mirror closely the corresponding geometric parameters measured for K[1b]. The B1-N3 distance, on the other hand is relatively short (1.387(4) Å; cf. 1.55 Å for the sum of the respective covalent radii, and 1.498(4)/1.510(4) Å for the other B-N distances associated with the diazaborolyl unit), suggesting that pdelocalization from the imide nitrogen into the B-centred heterocycle is structurally significant, (in contrast to Al=N p bonding).