Synthesis, structure and reactivity of NHC–nickel complexes containing carbonato ligands

• di-NHC nickel complexes containing carbonato ligands have been synthesized.
• The molecular structures have been determined.
• The nickel is surrounded by di-NHC and k2-catonato ligand on square plane.
• The length of linker has effect on the structures and catalytic activities.
• The complex with the longest linker showed the best catalytic activity.

Reactions of different alkane-bridged (n = 1–3) di-NHC precursors, bisimidazolium chlorides with the NiCl2 in presents of K2CO3 in acetonitrile give the corresponding 16-electron binuclear complexes of the type Ni(di-NHC)(μ-O)2CO in moderate yield. The molecular structures of 1–3 have been determined by X-ray crystallography, which revealed a cis-chelating di-NHC on a slightly distorted square-planar nickel center with κ2-cabonato ligand. The influence of the different di-NHC ligands on the structure and reactivity of the complexes has been studied. The catalytic properties of the complexes were investigated in the Kumada reaction for cross-coupling of phenylmagnesium bromide with a variety of aryl halides. The complex 3 which has the longest linker between two NHCs shows the best catalytic activity in these reactions.

A series of novel cis-chelating di-NHC nickel complexes containing carbonato ligands have been synthesized. The molecular structures have been determined. The nickel center is surrounded by di-NHC and κ2-catonato ligand on a slightly distorted square plane. The length of linker has effect on the structures and catalytic activities of these complexes. The complex with the longest linker showed the best catalytic activity for Kumada reactions.Figure optionsDownload as PowerPoint slide