Kinetic and Equilibrium Studies of Reactions of N-Heterocycles with Dimeric and Monomeric Oxorhenium(V) Complexes

✍ Scribed by James H. Espenson; S. Masoud Nabavizadeh

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 141 KB
• Volume: 2003
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200200601

✦ Synopsis

Abstract

Equilibrium constants have been evaluated for the reaction {MeReO(edt)}~2~ + 2 L ⇄ 2 MeReO(edt)L, where edt is 1,2‐ethanedithiolate and L is any of 13 N‐donor heterocyclic ligands. The values of K range from 1.37(27)×10^−2^ for pyrimidine to 1.95(6)×10^6^ for imidazole at 25 °C in chloroform. A successful correlation of log__K__ with log (K~a~) of HL^+^ was realized except in the case of the 2‐substituted ligands 2‐picoline and quinoline, where steric effects make K smaller than expected from the proton basicity of L. The kinetics of the same reactions were studied; the rate law for the reaction in the forward direction is given by −d[{MeReO(edt)}~2~]/d__t__ = {k~a~ + k~b~[L]}[L] × [{MeReO(edt)}~2~]. Except for 2‐picoline and quinoline, the major pathway is provided by the term that shows the quadratic dependence on [L]. Values of log (k~b~) also correlate with log K, and therefore necessarily with log (K~a~).