Issue 11, 2002

Base hydrolysis of macrocyclic chromium(iii) complexes. Importance of ion-pair formation for kinetics and mechanism

Abstract

A series of cis and trans complexes of the general formula [Cr(cyc)(OH2)X]2+, where cyc is the macrocyclic tetraamines meso- or rac- 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane and X = NCS, N3 and Cl, have been prepared in solution via anation of the diaqua complexes. The kinetics of the monodendate X ligand release in alkaline media have been studied at a range of temperatures and hydroxide concentrations at ionic strengths of 1.0 or 2.0 M using NaClO4, NaBr or NaCl as “inert” electrolytes. A higher order than linear dependence of the pseudo-first-order rate constant on the hydroxide concentration has been observed for all the systems investigated. These results have been rationalized in terms of specific ion-pair interactions between the macrocyclic chromium(III) reactants and counterions of the supporting electrolytes, followed by proton transfer in the hydroxide ion pair to give a reactive conjugate base.

Graphical abstract: Base hydrolysis of macrocyclic chromium(iii) complexes. Importance of ion-pair formation for kinetics and mechanism

Supplementary files

Article information

Article type
Paper
Submitted
13 Nov 2001
Accepted
26 Mar 2002
First published
26 Apr 2002

J. Chem. Soc., Dalton Trans., 2002, 2361-2365

Base hydrolysis of macrocyclic chromium(III) complexes. Importance of ion-pair formation for kinetics and mechanism

E. Madej, O. Mønsted and P. Kita, J. Chem. Soc., Dalton Trans., 2002, 2361 DOI: 10.1039/B110369E

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