Substitution reactions for the complex [Au(dien)Cl](2+) (dien = 3-azapentane-1,5-diamine) have been explored. Second-order rate constants, k(2), were predicted for chloride exchange and ring-opening processes using water and the stronger nucleophiles N-3(-) and SCN-. Under neutral and basic conditions, the deprotonated form of the complex [Au(dien-H)Cl](+) dominates and reacts promptly with all nucleophiles. The predicted reactivity order is SCN- (k(2) = 5.5 x 10(3) M-1 s(-1)) > N-3 (k(2) = 10.1 x 101 M-1 s(-1)) > H2O (k(2) = 0.4 M-1 s(-1)), in line with the experiment SCN (k(2) = 1.3 x 10(3) M-1 s(-1)) > N-3 (k(2) = 8.0 x 10(1) M-1 s(-1)) > H2O (k(2) = 0.6 M-1 s(-1)). Ring-opening is thermodynamically unfavourable but presents fast kinetics for stronger nucleophiles. (C) 2012 Elsevier B. V. All rights reserved.