The reactions of (Me3Al)2 with Me2AsNMe2, MeAs(NMe2)2 and As(NMe2)3 were studied as a function of time at room temperature and over the temperature range of -95 to 24°C by using 1H and 13C NMR spectroscopy. At -95°C, all the aminoarsines form the respective mono AlN bonded adducts. In addition, MeAs(NMe2)2 and As(NMe2)3 form bis AlN bonded adducts and As(NMe2)3 forms an AlAs bonded adduct. The bis adducts readily decompose and the AlAs bonded adduct dissociates at low temperature. All the mono AlN bonded adducts decompose by a pathway that transfers a methyl group from the aluminium to the arsenic atom, cleaves the AsN bond, and yields the next higher methyl homologue in the arsine series [MeAs(NMe2)2,Me2AsNMe2 or Me3As]. The bis AlN bonded adducts decompose to the next higher methyl homologue in the mono adduct series [MeAs(NMe2)NMe2·AlMe3 or Me2AsNMe2·AlMe3]. The other product in both cases is the unstable Me2AlNMe2, which dimerizes or undergoes further reaction with excess (Me3Al)2 or aminoarsine. The role of numerous competing side reactions and adduct/aminoarsine exchange equilibria in affecting the rate of adduct decomposition, overall rate of formation of the final product arsine, and final product distribution was established for each aminoarsine/(Me3Al)2 system. The initial stoichiometry of the reaction greatly influences the relative importance of the various reactions that occur in solution. Only when the moles of available Me3Al molecules equal those of Lewis base nitrogen sites, do the reactions proceed in a straightforward manner to give Me3As and (Me2AlNMe2)2. The results from the NMR studies were used to design a new, high yield synthetic route to Me3As. © 1990.