Methoxyaryl substituted palladium bis-NHC complexes – Synthesis and electronic effects

A series of methoxyphenyl substituted chelated bis-N-heterocyclic carbene palladium(II) complexes has been synthesized and characterized by cyclovoltammetry, spectroscopy (NMR, IR), solid state structures and investigated by quantum chemical calculations. The results confirm that a methoxy functionality in para position at the aryl substituent enhances the donor properties of the ligand compared to a methoxy group in ortho or meta position.

Graphical abstractThe effect of donor substitution by methoxy groups in 2-, 3-, and 4-position of the chelating phenylsubstituted bis-NHC ligand on the palladium center was investigated in detail by a variety of methods.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and characterization of new Pd(II) complexes with chelating NHC ligands. ► Synthesis and characterization of imidazoles and bis-imidazolium salts. ► Dependence of donor properties of the methoxy group on its position at the ring. ► CV-, IR-, NMR-data and DFT calculations explain the observed activity differences.