Preparation and Characterization of a Switchable Single-Component Chromium Trimerization Catalyst

Reaction of [(Ar)NPN(t-Bu)](2)Cr (2) with Me3Al afforded {[(Ar)NP(Me)N(t-Bu)]AlMe2}Cr{[(Ar)NP(Me)-(AlMe3)N(t-Bu)]AlMe(mu-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 degrees 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)(2)Al](2)O, the complex acts as a highly active polymerization catalyst.