Synthesis and characterization of hexacoordinate cobalt(III) complexes bearing three C,O-bidentate ligands

Hexacoordinated Co(III) complexes bearing three C,O-bidentate ligands (9a and 9b) were prepared from 1-bromo-2-(p-tolyloxymethyl)benzene (8a) and 1-bromo-2,6-bis(p-tolyloxymethyl)benzene (8b), respectively. Both complexes were stable in air at room temperature. X-ray analyses revealed that the structures of both complexes were essentially the same. According to variable temperature 1H NMR study, it was found that the two oxygen ligands on the same aromatic ring of 9b interchanged with each other.

Graphical abstractNovel Co(III) complex (9b) was prepared in 58% yield utilizing the C,O,O-pincer type ligand. X-ray crystallography clarified that the complex 9b has a hexacoordinated geometry with three C,O-bidentate ligands. In solution, a dynamic ligand exchange process was observed based on variable temperature NMR study.Figure optionsDownload full-size imageDownload as PowerPoint slide