1,3,5-Triazacyclohexane Complexes of Chromium as Homogeneous Model Systems for the Phillips Catalyst

Complexes of N-substituted 1,3,5-triazacyclohexanes with CrCl3 can be activated by MAO or PhNMe2H(B(C6F5)4)/AlR3 to give solutions that can polymerize and/or trimerize ethylene depending on the N-substituents R with activities and polymer products similar to those of the heterogeneous Phillips catalysts, α-olefins are selectively trimerized or copolymerized with ethylene. Variation of these substituents R showed a large dependence of the trimerization/polymerization ratio on branching in the N-substiruent. Spectroscopic studies show that the triazacyclohexane stays co-ordinated during the catalysis and that mono-nuclear metallacyclic complexes with a weakly coordinating anion in one coordination site are likely involved.