Stereochemical Control of Tricoordinate Copper(I) Complexes Based on N-(9-Alkyl-9-fluorenyl)-Substituted Heterocyclic Carbenes

International audienceA series of tricoordinate copper(I) complexes of general formula [Cu(F-Et-NHC)(2,2'-dipyridylamine)][BF4], in which EtF-NHC represents an imidazol-2-ylidene ligand bearing a 9-ethyl-9-fluorenyl N-substituent have been synthesised stepwise from appropriate N-arylimidazoles. All complexes are remarkably air-stable, both in solution and in the solid state. X-ray diffraction studies revealed that in three of the complexes the fluorenylidene plane and the dipyridylamine (dpa) unit undergo intramolecular pi-pi stacking. The resulting bending of the fluorenilydene plane towards the metal atom is likely to contribute to maintain the trigonal planar geometry of the [Cu-C,N,N] unit upon binding of exogenous substrates, thereby considerably increasing complex stability