Kinetics and mechanism of complex-formation reactions of ammonia and methylamine with copper(II) complexes in aqueous solution
Abstract
The complex-formation kinetics of copper(II) complexes with ammonia and methylamine was investigated by the temperature-jump relaxation technique. At 2 mol dm–3 ionic strength the forward rate constants (dm3 mol–1 s–1) for the studied reactions are: [Cu(NH3)]2++ NH3⇌[Cu(NH3)2]2+, (1.2 ± 0.1)× 108(7 °C); [Cu(ida)]+ NH3⇌[Cu(ida)(NH3)], (3.7 ± 0.3)× 108; [Cu(ida)]+ NMeH2⇌[Cu(ida)(NMeH2)], (8.7 ± 0.3)× 107; [Cu(mida)]+ NMeH2⇌[Cu(mida)(NMeH2)]. (5.4 ± 0.3)× 107(25 °C); ida = iminodiacetate, mida =N-methyliminodiacetate. The results presented and those from previous literature strongly suggest that specific interactions between the co-ordinated groups and the central metal ion do not modify the kinetics and mechanism of the complex formation. The kinetic data are consistent with the Eigen–Wilkins mechanism.