Copper(I) complexes of N-alkyl-substituted N-Heterocyclic carbenes

We report herein the synthetic routes to and spectroscopic and structural characterization of a variety of copper complexes bearing small alkyl-substituted N-heterocyclic carbene (NHC) ligands. Complexes of the type [Cu(NHC)X] and [Cu(NHC)2X] (X = Cl) were readily synthesized by reaction of Cu(I)Cl with a variety of the carbenes. The molecular structures of the [Cu(NHC)X] complexes all show two-coordinate Cu(I) atoms in nearly linear arrangements with C(NHC)CuCl angles very close to 180°. Utilizing the smallest alkyl carbene, Me2Im (= 1,3-di-methyl-imidazolin-2-ylidene), the compound adopts an ionic structure featuring a [Cu(Me2Im)2]+ cation and a [CuCl2]− anion. The reaction of copper(I) chloride with two equivalents of some NHCs (NHC = Me2Im, iPr2Im, iPr2ImMe2 [ = 1,3-di-iso-propyl-4,5-dimethylimidazolin-2-ylidene]) afforded complexes of the type [Cu(NHC)2X], which show a trigonal planar geometry with a propeller-like arrangement of the NHC ligands. Furthermore, complexes of the type [Cu(NHC)OR] (OR = OAc, OtBu, acac [ = acetylacetonato], DBM [ = dibenzoylmethanato]), were synthesized starting from [Cu(iPr2Im)X] (iPr2Im = 1,3-di-iso-propylimidazolin-2-ylidene), and characterized. The molecular structure of [Cu(NHC)DBM] clearly reveals the typical bidentate binding mode of this ligand. The compounds reported represent very useful starting points for the investigation of NHC copper(I) chemistry.Graphical abstractWe report the synthesis and detailed ...

Source: Journal of Organometallic Chemistry - November 30, 2018 Category: Chemistry Source Type: research