Simple synthesis of neutral and cationic Cu-NHC complexes

Abstract

A direct and practical synthetic route to N-heterocyclic carbene copper complexes of [(NHC)CuX] (X = halide) and [(NHC)2Cu]PF6 types using commercially available copper powder is described. A number of copper-NHC complexes have been obtained in a range of yields from 26 to 99%. The reactions take place in air without removal of moisture and oxygen, and the excess of copper powder can be easily removed via simple filtration after completion. The direct reactions of imidazolium salts and copper powder can also be performed in aqueous media avoiding tedious purification processes. The procedure is also suitable for gram-scale preparation.

Structure and spectroscopic properties of the dimeric copper(I) N-heterocyclic carbene complex [Cu2(CNCt-Bu)2](PF6)2

“…In the dimeric compound, the N atoms of the pyridine rings in the bridging bis-carbene ligands are directed towards the Cu I centres. The Cu-N distances are 2.5765 (17) (Cu1-N3), 2.8298 (18) (Cu1-N7), 2.6923 (18) (Cu2-N3) and 2.4220 (18) Å (Cu2-N7), indicating interaction (Liu et al, 2015). With regard to the pyridyl bridges, the NHC moieties are twisted to varying degrees, i.e.…”

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

“…5 ). Complex 6 crystallizes in the hexagonal space group R 3 c , which is different to the reported trinuclear copper(I) complex containing the symmetric 1,3-bis(2-pyridinylmethyl)benzimidazolylidene ligand (monoclinic, P 21/ c ) [ 33 ] and to the trinuclear copper(I) complex containing a symmetric 1,3-bis(triazole)benzimidazolylidene ligand (monoclinic, C 2/ c ) [ 38 ]. Three copper atoms are bridged by three N pyridine CN triazole NHC ligands forming a Cu 3 ring with three Cu–Cu–Cu angles of 60.0.…”

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

“…262 An improved correlation of -electron donation with the NMR coupling constant 1 JCSe has been reported. 262 However, the data for this index are considerably scarcer than those for the chemical shifts of 31 Р and 77 Se. Obviously, the chemical shift of 77 Se, as well as other NMR indices, are under the influence not only of electronic but also anisotropic shielding effects.…”

“…The differences in properties between the two can be very significant. Although in situ transformations are sometimes able to do surprising things (see, for example, the recently described 31 formation of carbene complexes of copper(I) from azolium salts and metallic copper), individual carbenes not only catalyse organic reactions but also open up new possibilities for organic synthesis. 32,33 The present article is concerned with the syntheses, structural studies and transformations of individual heterocyclic carbenes of the іmіdazole and triazole series, as well as their fused analogues.…”