In aqueous acidic media sodium azide and the orange-yellow title complex react quantitatively generating N2 gas along with a colourless solution of Ag+ ion and the ligand, ethylenebis(biguanide). The parent complex, [Ag(H2L)]3+, and one of its conjugate bases, [Ag(HL)]2+, participate in the reaction with N 3- as the kinetically reactive reductant. Ag+ has no catalytic effect. At 25.0 °C, I = 1.0 M (NaNO3), rate constants for the reactions [Ag(H2L)]3+ + N 3- and that for [Ag(HL)]2+ + N3 - are (12.3±0.5) and (3.8±0.6) M-1· S-1, respectively. The high rate constants along with the very low equilibrium constant (10-15 M-1) calculated for the first reaction strongly suggest inner-sphere redox mechanism. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.