Kinetics and mechanism of acid and base hydrolysis ofcis-chloro-(benzotriazole)bis(ethylenediamine)cobalt(III) andcis-chloro-(N-methylbenzotriazole)bis(ethylenediamine)cobalt(III) cations

Abstract

The kinetics of acid hydrolysis ofcis-[CoCl(btzH)(en)2]2+ andcis-[CoCl(btzMe)(en)2]2+ complexes (where btzH = benzotriazole, btzMe =N-methylbenzotriazole and en = ethylenediamine) have been investigated in HClO4 at ionic strength 1 = 0.25 mol dm−3 in the 30–40° range. In the 1.0 x 10−1 to 1.0 X 10−3 mol dm−3 acid strength range, the rate of aquation of the [CoCl(btzH)(en)2]2+ cation follows the relationship:-d ln[complex]/dt = k1 + k2KNH[H+]−1, where k1 and k2 are aquation rate constants of the acid independent and acid dependent steps respectively, and KNH is the acid dissociation constant of the coordinated benzotriazole.cis-[CoCl(btzMe)-(en)2]2+ undergoes acid independent hydrolysis presumably due to the absence of a labile N-H proton. The base hydrolysis could be followed for thecis-[CoCl(btzMe)(en)2]2+ complex only by measuring hydrolysis rates at 0°.