Reaction of Ph2P(8-CH2C9H6N)＝NBut (1) with 2 equiv of AlMe3 in toluene under reflux conditions afforded aluminum iminophosphorano(2-methyl-8-quinolyl)methandiide complex (2). The reaction proceeded via the intermediates of a coordination complex, [(AlMe3){Ph2P-(8-CH2C9H6N)＝NBut}] (3), and then an addition complex (4) of AlMe3 to the carbon-nitrogen double bond of the quinolyl ring of the neutral ligand. The coordination complex was converted to the singly deprotonated complex [(AlMe2){CH(8-C9H6N)(Ph2P＝NBut)}] (5) at 60℃, which further reacted with AlMe3 in toluene under reflux conditions to yield aluminum iminophosphorano (8-quinolyl) methandiide (6). The structures of complexes 2, 4, and 6 were proved by single-crystal X-ray diffraction techniques, and the five-coordinate complexes 3 and 5 were characterized by 27Al NMR spectroscopy.