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Contents Vol 64(8)

Abnormal N-heterocyclic Carbenes: More than Just Exceptionally Strong Donor Ligands

Anneke Krüger A and Martin Albrecht A B
+ Author Affiliations
- Author Affiliations

A School of Chemistry & Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.

B Corresponding author. Email: martin.albrecht@ucd.ie

Australian Journal of Chemistry 64(8) 1113-1117 https://doi.org/10.1071/CH11265
Submitted: 8 July 2011  Accepted: 18 July 2011   Published: 19 August 2011

Abstract

Complexes comprising a so-called abnormal carbene ligand, which displays pronounced mesoionic character, have recently been shown to be competent catalyst precursors for bond activation processes and oxidative transformations, including base-free alcohol oxidation and water oxidation. In this highlight we propose that these abnormal carbene ligands are not just useful spectator ligands but also actively participate in the bond activation step. This mode of action is partially based on the exceptionally strong donor properties of the ligand and, specifically, on the mesoionic character of these abnormal carbenes. The mesoionic properties provide a reservoir for charges and holes and thus induce efficient ligand-metal cooperativity, which is beneficial in particular for oxidation catalysis that involves concerted proton and electron transfer processes.


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