"Hummingbird" Behaviour of N-Heterocyclic Carbenes Stabilises Out-of-Plane Bonding of AuCl and CuCl Units

作者：Teci Matthieu; Brenner Eric^*; Matt Dominique; Gourlaouen Christophe; Toupet Loic

来源：Chemistry - A European Journal, 2015, 21(31): 10997-11000.

DOI：10.1002/chem.201500840

• copper
• density functional calculations
• gold
• hydrogen bonding
• N-heterocyclic carbenes
• noncovalent interactions

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 degrees) 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 center dot center dot center dot Au interactions involving aliphatic and aromatic H atoms of the NHC wingtips. Weak, intermolecular Cl center dot center dot center dot H bonds are likely to cooperate with the H center dot center dot center dot 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.

• 出版日期2015-7-27