Chromium(III) complexes with terdentate 2,6-bis(azolylmethyl)pyridine ligands: Synthesis, structures and ethylene polymerization behavior

Reactions of 2,6-bis(bromomethyl)pyridine with 3,5-dimethylpyrazole and 1H-indazole yield the terdentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (5) and 2,6-bis(indazol-2-ylmethyl)pyridine (6). The molecular structure of the new compound 6 was determined by single-crystal X-ray diffraction. These ligands react with the CrCl3(THF)3 complex in THF to form neutral complexes of general formula [CrCl3{2,6-bis(azolylmethyl)pyridine-N,N,N}] (7, 8) which are isolated in high yields as stable green solids and characterized by means of elemental analysis, magnetic moments, IR, and mass spectroscopy. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active in the polymerization of ethylene.

Graphical abstract2,6-Bis(azolylmethyl)pyridine ligands are obtained by reaction of 2,6-bis(bromomethyl)pyridine with 3,5-dimethylpyrazole and 1H-indazole. The molecular structure of the ligand 2,6-bis(indazol-2-ylmethyl)pyridine was determined by single-crystal X-ray diffraction. These ligands react with the CrCl3(THF)3 complex to form octahedral complexes formula [CrCl3{2,6-bis(azolylmethyl)pyridine-N,N,N}]. Theoretical calculations show that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active in the polymerization of ethylene.Figure optionsDownload full-size imageDownload as PowerPoint slide