Mechanistic Insights of a Concerted Metalation–Deprotonation Reaction with [Cp*RhCl₂]₂

Abstract

The effect of the carboxylate used in a concerted metalation–deprotonation reaction is probed and shows a direct correlation of p K a to observed rate up to a p K a of 4.3, where the rate drops off at higher p K a . The rate of the C–H activation of 2-(4-methoxyphenyl)pyridine with [Cp*RhCl 2 ] 2 and carboxylate follows first-order kinetics in the active metal species, Cp*RhCl(κ 2 -OAc), and zero-order kinetics in substrate when in a 1:1 ratio. There is a first-order dependence on substrate observed when excess substrate is present. The evaluation of the mechanism using kinetic studies allowed for a mechanistic proposal in which a second Ph′Py coordinates prior to the rate-determining C–H activation.