The polymerization of norbornenes has been investigated using a variety of (π-allyl) Group 10 initiators. However, there are few efficient metal-catalyzed polymerization reactions involving nonpolar monomers such as norbornene, butadiene, and ethylene with polar monomers, which increase the value of the polymer. There is great interest in polynorbornene because it possesses good mechanical strength, high chemical resistance, optical transparency, high glass transition temperatures, and large refractive indices. We report the synthesis and characterization of (π-allyl) Group 10 (Ni, Pd) cations containing bulky dialkylbiaryl phosphine ligands. Vinyl addition polymerization of norbornene is initiated using cationic (π-allyl)nickel complexes without a cocatalyst. Polynorbornene was obtained in 26-98% yield, where the lowest yields were observed when utilizing initiators without substituents on the lower aryl ring of the biaryl phosphine ligand, while the highest yields were obtained when using initiators bearing electron donating methoxy substituents on the lower aryl ring of the biaryl phosphine ligand. In contrast, polymerization of norbornene is not observed using (π-allyl) palladium cations containing dialkylbiaryl phosphine ligands. An agostic species as determined by <sup>1</sup>H NMR spectroscopy and a coupling product between the allyl moiety and norbornene are observed. Described here is our initial progress using a synergistic computational and experimental approach to evaluate the mechanism of insertion when norbornene reacts with these palladium cations along with a binding study to investigate the strength of the pendent arene fragment to the palladium or nickel center.<br/><br/>

Catalytic and mechanistic evaluation of norbornene polymerization initiated by cationic (π-Allyl) group 10 complexes containing dialkylbiaryl phosphine ligands

253rd National Meeting (2017)

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