Kinetics of oxidation of azide by [ethylenebis(biguanide)]silver(III) in aqueous acidic media

In aqueous acidic media sodium azide and the orange-yellow title complex react quantitatively generating N-2 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(H2L)](3+), participate in the reaction with N-3(-) as the kinetically reactive reductant. Ag+ has no catalytic effect. At 25.0 degreesC, I = 1.0 M (NaNO3), rate con-stants for the reactions [Ag(H2L)](3+) + N-3(-) and that for [Ag(HL)(2+) + N-3(-) 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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).