Nickel(II) halide complexes of novel chelating bidentate benzimidazole-based N-heterocyclic carbenes have been prepared from Ni(OAc)2 and bisbenzimidazolium salts. Single-crystal X-ray structure determination on four complexes revealed a cis-geometry on a square-planar nickel center. The complexes are active catalysts for the Kumada coupling of 4-chloroanisole and 4-bromoanisole with phenylmagnesium chloride. The most active catalyst gives a complete conversion of 4-bromoanisole within 75 min with a selectivity to 4-methoxybiphenyl of 82% and a complete conversion of 4-chloroanisole in less than 14 h with a selectivity to 4-methoxybiphenyl of 99%.

The preparation of new manganese and iron complexes with the general formula [M(tripod)(anion)] is described, where M = Fe III or Mn III , "tripod" is a dianionic tetradentate tripodal ligand and the anion is a chelating β-diketonate, 8-oxyquinoline or acetate. The synthesis of this type of complexes was found to be straightforward, which allows for the preparation of a large variety of such coordination compounds. The complexes are characterised by X-ray crystallography, infrared spectroscopy, UV/Vis spectroscopy, cyclic voltammetry and elemental analysis. A correlation between the ligand sets and the electron density at the metal centre in the complexes is

The synthesis and characterization of novel nickel(II) complexes bearing two bidentate N-heterocyclic carbene ligands functionalized with anionic N-donor moieties are described. Two different N-donor groups are employed, namely amido and benzimidazolato moieties. The solid-state structures of three of these complexes have been determined by X-ray crystallography. The amido-functionalized low-spin, square-planar Ni(II) complexes exhibit a cis geometry around the metal centre, while the benzimidazolato-functionalized complex crystallizes as the trans isomer. The activity of these novel complexes in the Kumada cross-coupling of phenylmagnesium chloride with 4-chloroanisole and 4-fluoroanisole was investigated. One of the benzimidazolato-functionalized complexes shows the highest activity in this reaction reported to date, yielding the desired product in quantitative yields within 30 min (4-chloroanisole), or 150 min (4-fluoroanisole) with only 1 mol% catalyst.

A number of nickel(II) dihalide complexes with small monodentate N-heterocyclic carbene ligands was synthesized and tested for their catalytic activity in the hydrosilylation of internal alkynes. The nickel(0) active species was obtained from the starting nickel(II) complex by reduction with diethylzinc. In all cases the catalytic reaction yielded the syn product selectively. The fastest catalysts reached full conversion