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

Reaction of [(Ar)NPN( t -Bu)] 2 Cr ( 2 ) with Me 3 Al afforded {[(Ar)NP(Me)N( t -Bu)]AlMe 2 }Cr{[(Ar)NP(Me)(AlMe 3 )N( t -Bu)]AlMe(μ-Me)} ( 3 ), in which the ligandʼs P atom has been alkylated and one AlR 2 residue retained by the chelating framework. One of the two ligands also retained an additional Me 3 Al 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) 2 Al] 2 O, the complex acts as a highly active polymerization catalyst.