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Updated: Mar 7, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Quantifying and understanding the steric properties of N-heterocyclic carbenes
Adrián Gómez-Suárez1, David J Nelson2, Steven P Nolan3
1Organic Chemistry Institute, WWU Münster, Corrensstrasse 40, 48149 Münster, Germany.
Abstract:
This Feature Article presents and discusses the use of different methods to quantify and explore the steric impact of N-heterocyclic carbene (NHC) ligands. These include (a) the percent buried volume (%Vbur), which provides a convenient single number to measure steric impact and (b) steric maps, which provide a graphical representation of the steric profile of a ligand using colour-coded contour maps. A critical discussion of the scope and limitations of these tools is presented, along with some examples of their use in organometallic chemistry and catalysis. This Article should provide all users of NHCs, from organic, organometallic, and inorganic chemistry backgrounds, with an appreciation of how these tools can be used to quantify and compare their steric properties.
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