Multinuclear NMR Spectroscopic Characterization of a Fluorinated Enolatoimine Titanium Polymeryl Species in the Living Ethylene-coNorbornene Polymerization

A multinuclear NMR spectroscopic study was performed to assess the nature of species responsible for living ethylene (E)-norbornene (N) copolymerization reaction using the fluorinated enolatoimine titanium complex [Ti(?2-N,O-{2,6-F2C6H3N?C(Me)C(H)C(CF3)O})2Cl2] (1) activated with dry methylaluminoxane (d-MAO). The analysis involved (i) the catalytic system (1 with MAO); (ii) the species formed after simultaneous addition of 13C-enriched ethylene and norbornene and after further addition of 13C-enriched ethylene; and (iii) species formed during norbornene homopolymerization. The results supported the existence of noncovalent interactions of ortho-fluoroaryl substituents with the titanium center, which contribute to the living character of the copolymerization reaction.