Tridentate P∧N∧P chromium complexes: Synthesis, characterization and their ethylene oligomerization and polymerization

Abstract

A series of chromium(III) complexes ligated by the 2-(diphenylphosphino)-N-[2-(diarylphosphino)benzylidene] anilines (P∧N∧P) and 2-(diphenylphosphino)-N-[2-(diarylphosphino)benzyl]benzenamine (P∧N∧P) were synthesized and characterized by elemental and spectroscopic analyses as well as the X-ray single-crystal crystallography, revealing both chromium complexes 1a and 2a as the six-coordinated distorted octahedral geometry. Upon activation with MAO or AlEtCl2, these chromium complexes performed good catalytic activities for ethylene oligomerization and polymerization. Unique properties were observed for two typical chromium complexes due to the different coordinated nitrogen from imino and secondary amino group in the ligands. The chromium complexes 1a~1e bearing 2-(diphenylphosphino)-N-[2-(diarylphosphino)benzylidene] anilines preceded ethylene polymerization without observing any oligomers, meanwhile chromium complexes 2a~2e coordinated with 2-(diphenylphosphino)-N-[2-(diarylphosphino)benzyl]benzenamines performed major ethylene trimerization with excellent selectivity towards α-olefins. © 2013 Chinese Chemical Society and SIOC, CAS.