Preparation and characterization of a switchable single-component chromium trimerization catalyst

Abstract

Reaction of [(Ar)NPN(t-Bu)]2Cr (2) with Me3Al afforded {[(Ar)NP(Me)N(t-Bu)]AlMe2}Cr{ [(Ar)NP(Me)-(AlMe 3)N(t-Bu)]AIMe(μ-Me)) (3), in which the ligand's P atom has been alkylated and one AlR2 residue retained by the chelating framework. One of the two ligands also retained an additional Me3Al unit via coordination to the alkylated P atom. Complex 3 provides the first case of a selective ethylene trimerization catalyst with high activity and excellent selectivity, producing 1-hexene upon exposure to ethylene at 80°C. Furthermore, upon treatment with MAO, complex 3 acts as a nonselective catalyst, producing a statistical mixture of oligomers with the highest ever observed activity. In addition, upon treatment with [(i-Bu)2Al]2O, the complex acts as a highly active polymerization catalyst. © 2008 American Chemical Society.