Abstract
The kinetics sarcosine complexation with nickel(II), cobalt(II) and copper(II) have been determined by temperature jump. The reactions were of the type ML„_i + L ^ ML „(kn, k-n), where M = Ni2+, Co2+, or Cu2+, L refers to the anionic form of the ligand, and = 1, 2, or 3. At ionic strength 0.1 Mand 25° the rate constants are: Ni2+, k\ = 1.3 X 104 A/-1 sec-1, k-1 = 4.1 X Í0-2 sec-1, k2 = 1.2 X 104 M-1 sec-1, fc_2 = 0.50 sec-1, k3 ~
5 X 103 M-1 sec-1, k_3 ~ 5 sec-1; Co2+, ki = 9.2 X 105 M-1 sec-1, k-1 = 57 sec-1, fe = 1,5 X 106 A/-1 sec-1, k- = 5.7 X 102 sec-1; Cu2+, ki = 2.8 X 109 M-1 sec-1, k_i = 32 sec-1, k2 = 1.0 X 108 M-1 sec-1, k_2 = 22 sec-1. The cobalt kinetics follow the dissociative mechanism for sarcosine. However, in the nickel complexa- tion kinetics, formation of the mono and bis complexes appears to be relatively slow, indicating that the N-bonded methyl group in sarcosine has an influential role. As observed with cobalt, formation of the copper-sarcosinate complex is normal. Unlike cobalt, the formation of the bis complex is relatively slow.