“Hummingbird” Behaviour of N‐Heterocyclic Carbenes Stabilises Out‐of‐Plane Bonding of AuCl and CuCl Units |
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Authors: | Matthieu Teci Dr Eric Brenner Dr Dominique Matt Christophe Gourlaouen Loic Toupet |
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Institution: | 1. Laboratoire de chimie inorganique moléculaire et catalyse Institut de chimie UMR 7177 CNRS, Université de Strasbourg (France);2. Laboratoire de Chimie Quantique, Institut de chimie UMR 7177 CNRS, Université de Strasbourg 1 rue Blaise Pascal, 67008 Strasbourg (France);3. Institut de Physique de Rennes, UMR 6251 CNRS, Université de Rennes?1, Campus de Beaulieu, 35042 Rennes cedex (France) |
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Abstract: | An N‐heterocyclic carbene substituted by two expanded 9‐ethyl‐9‐fluorenyl groups was shown to bind an AuCl unit in an unusual manner, namely with the Au?X rod sitting out of the plane defined by the heterocyclic carbene unit. As shown by X‐ray studies and DFT calculations, the observed large pitch angle (21°) arises from an easy displacement of the gold(I) atom away from the carbene lone‐pair axis, combined with the stabilisation provided by weak CH???Au interactions involving aliphatic and aromatic H atoms of the NHC wingtips. Weak, intermolecular Cl???H bonds are likely to cooperate with the H???Au interactions to stabilise the out‐of‐plane conformation. A general belief until now was that tilt angles in NHC complexes arise mainly from steric effects within the first coordination sphere. |
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Keywords: | copper density functional calculations gold hydrogen bonding N‐heterocyclic carbenes noncovalent interactions |
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