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

A series of tricoordinate copper(I) complexes of general formula [Cu(Et F-NHC)(2,2′-dipyridylamine)][BF4], in which Et F-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 π–π 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.