Issue 10, 2016

Tandem vinyl insertion-/ring-opening metathesis copolymerization with ansa-6-[2-(dimesitylboryl)-phenyl]pyrid-2-ylamido zirconium complexes: role of trialkylaluminum and MAO

Abstract

The novel dialkylzirconium complexes L′ZrR2, (R = CH3, Bn = benzyl, CH2SiMe3, L′ = Me2Si{η5-tetramethylcyclopentadienyl}{6-[2-(dimesitylboryl)phenyl]pyrid-2-ylamido}) were synthesized. Upon activation with 1 equiv. of [Ph3C]+[B(C6F5)4], both L′Zr(CH3)2 and L′Zr(Bn)2 are quantitatively converted in situ into [L′Zr(CH3)]+[B(C6F5)4] and [L′Zr(Bn)]+[B(C6F5)4] while only 28 mol% conversion is observed with L′Zr(CH2SiMe3)2. The aluminum-free cationic catalysts [L′Zr(CH3)]+[B(C6F5)4], [L′Zr(Bn)]+[B(C6F5)4] and [L′Zr(CH2SiMe3)]+[B(C6F5)4] initiate ring-opening metathesis polymerization (ROMP) of NBE to form predominantly cis-poly(NBE)ROMP. Upon activation with [Ph3C]+[B(C6F5)4] and AliBu3, L′Zr(CH3)2, L′Zr(Bn)2 and L′Zr(CH2SiMe3)2 also exhibit moderate catalytic activity in the copolymerization of ethylene (E) with NBE. The resulting copolymers do not contain any ROMP-derived poly(NBE), which is in stark contrast to the complexes’ homopolymerization propensity for NBE. Upon activation with methylalumoxane (MAO), L′Zr(CH3)2 and L′Zr(Bn)2 produce pure vinyl-insertion polymerization-derived poly(NBE)-co-poly(E) while L′Zr(CH2SiMe3)2 allows for the synthesis of predominantly trans-poly(NBE)ROMP-co-poly(NBE)VIP-co-poly(E)-based copolymers via an α-H+ elimination/addition process. Our findings are discussed on the basis of the instability of the alkylidenes in the presence of E and the blocking effect of aluminum alkyls on ROMP via coordination to the pyridyl-moiety in the cationic complexes.

Graphical abstract: Tandem vinyl insertion-/ring-opening metathesis copolymerization with ansa-6-[2-(dimesitylboryl)-phenyl]pyrid-2-ylamido zirconium complexes: role of trialkylaluminum and MAO

Supplementary files

Article information

Article type
Paper
Submitted
15 Jan 2016
Accepted
14 Feb 2016
First published
15 Feb 2016
This article is Open Access
Creative Commons BY license

Polym. Chem., 2016,7, 1987-1998

Tandem vinyl insertion-/ring-opening metathesis copolymerization with ansa-6-[2-(dimesitylboryl)-phenyl]pyrid-2-ylamido zirconium complexes: role of trialkylaluminum and MAO

M. Wang, D. Wang, L. Widmann, W. Frey and M. R. Buchmeiser, Polym. Chem., 2016, 7, 1987 DOI: 10.1039/C6PY00078A

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