A new vanadium (III) complex of 2,6-bis(3,5-diphenylpyrazol-1-ylmethyl)pyridine as a catalyst for ethylene polymerization.

The tridentate ligand 2,6-bis(3,5-diphenylpyrazol-1-ylmethyl)pyridine, abbreviated as 2,6-[(3,5-ph₂pz-CH₂)₂-py], a new pyridine-pyrazole derivative, was prepared from 2,6-bis(bromomethyl)pyridine and 3,5-diphenylpyrazole. The ligand was characterized by means of elemental analyses, ATR-IR, ¹H- and ¹³C-NMR spectroscopy and single crystal X-ray crystallography. Using this ligand, a new mononuclear vanadium (III) complex, {2,6-[(3,5-ph₂pz)CH₂]₂py}VCl₃ was prepared and characterized by elemental analysis, ATR-IR and HR-MS. The complex was investigated as a catalyst for ethylene polymerization and compared with 2,6-[(3,5-Me₂pz)CH₂]₂py}VCl₃ to explore the effect of the substituent on the pyrazolyl rings on ethylene polymerization. High catalytic activity was observed at ambient temperature. After treatment with AlEtCl₂, these complexes showed high activity for ethylene polymerization converting ethylene to highly linear polyethylene and affording high molecular weight polymers (up to 1.0 × 10⁶ g/mol) with unimodal molecular weight distributions.