Homo- and Copolymerization of Ethylene with Norbornene Catalyzed by Vanadium(III) Phosphine Complexes.

ABSTRACT: Herein, we report the homo- and co-polymerization of ethylene (E) with norbornene (NB) catalyzed by vanadium(III) phosphine complexes of the type VCl₃(PMe_nPh_3-n)₂ [n = 2 (1a), 1 (1b)] and VCl₃(PR₃)₂ [R = phenyl (Ph, 1c), cyclohexyl (Cy, 1d), tert-butyl (tBu, 1e)]. In the presence of Et₂AlCl and Cl₃CCOOEt (ETA), 1a-1e exhibit good activities for the polymerization of ethylene, affording linear, semicrystalline PEs with a melting temperature of approximately 130 °C. Mainly alternating copolymers with high comonomer incorporation were obtained in the E/NB copolymerization. A relationship was found between the electronic and steric properties of the phosphine ligands and the catalytic performance. Overall, the presence of electron-withdrawing ligand substituents increases the productivity, complexes with aryl phosphine (weaker ?-donor character) exhibiting a higher (co)polymerization initiation rate than those with alkyl phosphines (stronger ?-donor character). Steric effects also seem to play a key role since 1d and 1e, having large size phosphines (PCy₃ ? = 170° and PtBu₃ ? = 182°, respectively) are more active than 1a (PMe₂Ph ? = 122°). In this case, the larger size of PtBu₃ and PCy₃ likely compensates for their higher donor strength compared to PMe₂Ph.

SUBMITTER: Zanchin G 

PROVIDER: S-EPMC6600629 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature