The reactions of Me2AsNR2 with Et2AsAsEt2, and of Et2AsNR2 with Me2AsAsMe2 (R = Me or Et), were investigated over the temperature range 24-75°C by using 1H and 13C NMR spectroscopy. The NMR data indicate the initial formation of the unsymmetrical diarsine, Me2AsAsEt2, and the respective dialkylamino-dialkylarsine, Et2AsNR2 or Me2AsNR2. The Me2AsAsEt2 then undergoes symmetrization to yield Me2AsAsMe2 and Et2AsAsEt2. Additional competitive reactions involving AsAs-AsNandAsN-AsN systems also occur in the reaction mixture. In each case, the percentage distribution of products and reactants in the studied systems at equilibrium is independent of temperature within experimental measurement. The reaction rates are dependent upon the nature of R and the alkyl group in the diarsine. In addition, equilibrium constants for several competitive reactions have been determined. © 1987.