A single crystal of the azidoalane [Me2N(CH2)3]AltBu(N3) (1a), grown in a capillary using a miniature zone melting procedure, was studied by x-ray anal. Compd. 1a (C9H21AlN4) is a monomeric species in the solid state, which crystallizes in the monoclinic space group P21 with a = 6.8560(14) A, b = 12.251(3) A, c 7.786(2) A, b 108.51(3) Deg and Z = 2. The results of the x-ray structural detn. are compared with the calcd. structure of 1a (HF/6-31G(d) and B3LYP/6-31G(d) level of theory). Whereas the overall agreement between the measured and calcd. structure is good, the Al-N donor-bond length differs by 11 and 12 pm at the HF and B3LYP level, resp. To evaluate the effects of a polar environment on the mol. structure of 1a self-consistent reaction field (SCRF) calcns. at the HF and B3LYP level with the 6-31G(d) basis set were performed.