Mechanism of propylene insertion using bis(phenoxyimine)-based titanium catalysts: an unusual secondary insertion of propylene in a group IV catalyst system.
A highly regioselective secondary enchainment of propylene in a group IV catalyst system is reported. End-group analysis of polypropylene formed using the phenoxyimine-based titanium catalysts revealed a reversal in the regioselectivity of insertion for this class of catalysts. To the best of our knowledge, bis(phenoxyimine)-based titanium complexes are the only known group IV catalysts that insert propylene with exclusive 2,1-regiochemistry. Insertion of propylene into the initiating titanium hydride occurs with high 1,2-regiochemistry. Subsequent insertions into primary titanium alkyls are regiorandom, while insertions into secondary titanium alkyls proceed with high 2,1-regioselectivity. Cyclopolymerization and ethylene/propylene copolymerization strategies are employed to support this proposal.
Hustad
Phillip D
PD
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Tian
Jun
J
Coates
Geoffrey W
GW
D000475:Alkenes / Q000737:chemistry*; D002247:Carbon Isotopes; D002384:Catalysis; D006844:Hydrocarbons, Cyclic / Q000138:chemical synthesis; D007097:Imines / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009942:Organometallic Compounds / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
D000475:Alkenes; D002247:Carbon Isotopes; D006844:Hydrocarbons, Cyclic; D007097:Imines; D009942:Organometallic Compounds; C013658:propylene; D014025:Titanium