Further studies on the effects of substituents at the Cp and salicyladiminato ligands of half-sandwich chromium(III) complexes on their catalytic properties for ethylene polymerization

• New half-sandwich chromium (III) olefin polymerization catalysts with various Cp ligands.
• Production of high molecular weight polyethylene in the form of spherical particles.
• Activation of these catalysts with AlR3 cocatalysts.
• Remarkable effects of the Cp ligand on the catalytic performances of these catalysts observed.

A series of new half-sandwich chromium(III) complexes Cp′[2-R1-6-(CHNR2)C6H2O]CrCl [R1 = iPr (1), tBu (2, 3, 4, 5); R2 = iPr (2, 4, 5), tBu (1, 3); Cp′ = C5H5(1, 2, 3), C5H2Ph3 (4), C5Me4Ph(5)] were synthesized from the reactions of Cp′CrCl2(THF) with corresponding salicyladiminato lithium. All complexes were characterized by elemental analyses and the structures of complexes 1, 2, 3 and 5 were determined by X-ray diffraction analysis. These complexes show moderate catalytic activities for ethylene polymerization upon activation with a relatively small amounts of AlMe3 or AlEt3, producing high molecular weight polyethylene in the form of spherical particles. Under similar conditions, the catalytic activity of complexes carrying a same salicylaldiminato ligand changes with the cyclopentadienyl ligand in the order Me5Cp > Me4PhCp > 1,2,4-Ph3Cp > Cp. The catalytic activity of these catalysts is also affected significantly by the AlR3 cocatalyst in the order AlMe3 > AlEt3.

A series of new half-sandwich chromium (III) complexes with various Cp and salicyladiminato ligands were synthesized and studied as catalysts for ethylene polymerization. Catalysts with moderate activities were obtained. The catalytic activity of these catalysts is significantly affected by the Cp ligand.Figure optionsDownload as PowerPoint slide