Search:
Computing and Library Services - delivering an inspiring information environment

The kinetics and mechanism of the organo-iridium catalysed racemisation of amines

Stirling, Matthew John, Mwansa, Joseph M., Sweeney, Gemma, Blacker, John and Page, Michael I. (2016) The kinetics and mechanism of the organo-iridium catalysed racemisation of amines. Organic & Biomolecular Chemistry. ISSN 1477-0520

[img] PDF - Published Version
Restricted to Repository staff only until 28 June 2017.

Download (858kB)

Abstract

The dimeric iodo-iridium complex [IrCp*I2 ]2
(Cp*=pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the orresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration.
Low temperature 1H NMR data is consistent with the formation of a 1:1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp* results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect kH/kD = 3.24 ndicating that hydride transfer is involved in the rate-limiting step.

Item Type: Article
Subjects: Q Science > QD Chemistry
Schools: School of Applied Sciences
Related URLs:
Depositing User: Elizabeth Boulton
Date Deposited: 30 Jun 2016 13:32
Last Modified: 10 Dec 2016 12:18
URI: http://eprints.hud.ac.uk/id/eprint/28846

Downloads

Downloads per month over past year

Repository Staff Only: item control page

View Item View Item

University of Huddersfield, Queensgate, Huddersfield, HD1 3DH Copyright and Disclaimer All rights reserved ©