The reactions of R2PPR2 (R = Me, Et, Ph) and (MeP)5 with Me3-nAs(NMe2)n (n = 1, 2, 3) and of Me2PPMe2 with Me2AsNR′2 (R′ = Et, Prn, and Pri) were investigated as a function of time at room temperature using 1H and 31P NMR spectroscopy. For the diphosphine/Me2AsNR′2 reactions, the NMR spectral data suggest a reaction pathway involving the initial formation of R2PAsMe2 and the respective acyclic dialkylaminophosphine, R2PNR′2. The PAs intermediate then symmetrizes to R2PPR2 and Me2AsAsMe2, the parent aminoarsine is completely consumed, and additional R2PNR′ is formed. The relative rate of aminophosphine production is dependent upon the nature of the substituent on the phosphorus and nitrogen atoms. For systems involving MeAs(NMe2)2 and As(NMe2)3 as reactants, the intermediates could not be characterized, but the products were the expected aminophosphine and (MeAs)5 or elemental arsenic, respectively. (MeP)5 reacts to give MeP(NMe2)2 and the expected AsAs bonded species. A comparison of the reactivity of these systems with analogous diarsine/aminoarsine systems is discussed. The results of the NMR study were utilized in designing a convenient, high yield, synthetic route to acyclic aminophosphines. © 1988.