The synthesis of a novel tetrameric gallane, [HCIGaN3](4) (1), with a heterocyclic cyclooactane-like structure has been demonstrated. A single-crystal X-ray study reveals that the molecule consists of eight-membered Ga4N4 rings with Ga atoms bridged by the alpha-nitrogens of the azide groups. [HClGaN3](4) crystallizes in the tetragonal space group space group P4(2)bc, with a = 17.920(3) Angstrom, c = 10.782(3) Angstrom, V = 3462(2) Angstrom(3), and Z = 8. On the basis of the mass spectrum, the vapor of the compound consists of the trimer [HClGaN3](3), which is a low-temperature molecular source for growth of GaN layers on sapphire and Si substrates at 500 degrees C. Solid 1 decomposes exothermically at 70 degrees C to yield bulk nanocrystalline wurtzite and zinc blende GaN. The reaction between H2GaCl and LiN3 yields the analogous and extremely simple azidogallane (H2GaN3), (2), which is used to deposit crystalline GaN films at 450 degrees C. Compound 2 is considerably more reactive than 1, and its decomposition, often initiated at room temperature, yields pure and crystalline nitride material of unusual morphology and microstructure.