Eva Jürgens

Synthesis of copper(II) and gold(III) bis(NHC)-pincer complexes

Abstract CuII and AuIII chlorido complexes bearing the bis(NHC) carbazolide pincer ligand (bimca) were synthesized by transmetallation from the respective lithium complex [Li(bimca)] (NHC=N-heterocyclic carbene). In the case of copper, two different molecular structures were obtained depending on the copper source. With Cu(II) chloride the paramagnetic mononuclear [Cu(bimca)Cl] complex is formed and has been characterized by EPR spectroscopy and X-ray structure analysis, while copper(I) chloride leads under oxidation to a dinuclear structure in which two cationic [CuII(bimca)] moieties are bridged by one chlorido ligand. The positive charge is compensated by the [CuCl2]− counter ion, as proven by X-ray structure analysis. Transmetallation of [Li(bimca)] with AuCl3 leads to the [Au(bimca)Cl]+ complex with a tetrachloridoaurate counter ion.

Optimised synthesis of monoanionic bis(NHC)-pincer ligand precursors and their Li-complexes

Herein we report the optimised synthesis of a versatile bis(imidazole)carbazole framework 4, a precursor to our previously reported C–N–C bis(NHC) pincer ligand, bimca. We have also used 4 as a basis for constructing a library of fully characterised bis(imidazolium) salt pre-ligands which vary the steric and electronic parameters of the subsequently formed NHC moieties. Lithium bis(NHC)carbazolide complexes Li(bimcaR) were generated from their parent bis(imidazolium)carbazole salts, and their behavior in solution and the solid state is discussed.