Issue 25, 2013

Chiral and achiral (imino)phenoxy-based cationic group 4 non-metallocene complexes as catalysts for polymerization of renewable α-methylene-γ-butyrolactones

Abstract

Protonolysis of M(Bn)4 (M = Zr, Ti; Bn = benzyl) with equimolar 2,4-di-tert-butyl-6-[(2,6-diisopropylphenylimino)methyl]phenol [(2,6-iPr2C6H3)N[double bond, length as m-dash]C(3,5-tBu2C6H2)OH] in toluene at −30 °C to 25 °C cleanly affords the corresponding achiral (imino)phenoxy-tribenzyl complexes, [(2,6-iPr2C6H3)N[double bond, length as m-dash]C(3,5-tBu2C6H2)O]Zr(Bn)3 (1) and [(2,6-iPr2C6H3)N[double bond, length as m-dash]C(3,5-tBu2C6H2)O]Ti(Bn)3 (2). A chiral dibenzyl complex 3 incorporating the unsymmetric, tetradentate amino(imino)bis(phenoxy) ligand, [2,4-Br2C6H2(O)(6-CH2(NC5H9))CH2N[double bond, length as m-dash]CH(2-adamantyl-4-MeC6H2O)]Zr(Bn)2 (3), has also been prepared using the same protonolysis protocol. Abstractive activation of 1 with B(C6F5)3·THF in CD2Cl2 at room temperature (RT) affords clean, quantitative formation of the corresponding zirconium cation [((2,6-iPr2C6H3)N[double bond, length as m-dash]C(3,5-tBu2C6H2)O)Zr(Bn)2(THF)]+[BnB(C6F5)3] (4). Likewise, benzyl abstraction of 2 with B(C6F5)3·THF in CD2Cl2 at RT generates the cationic titanium complex [((2,6-iPr2C6H3)N[double bond, length as m-dash]C(3,5-tBu2C6H2)O)Ti(Bn)2(THF)]+[BnB(C6F5)3] (5), accompanied by a small amount of decomposed species as a result of C6F5 transfer. The dibenzyl cations 4 and 5 have been characterized spectroscopically, and their structures have been confirmed by single crystal X-ray diffraction analysis. Characteristics of the coordination polymerization of renewable α-methylene-γ-butyrolactone monomers by the cationic catalysts derived from achiral complexes 1 and 2 as well as chiral complex 3 have been investigated, representing the first study of such polymerization by non-metallocene catalysts.

Graphical abstract: Chiral and achiral (imino)phenoxy-based cationic group 4 non-metallocene complexes as catalysts for polymerization of renewable α-methylene-γ-butyrolactones

Supplementary files

Article information

Article type
Paper
Submitted
15 Feb 2013
Accepted
07 Mar 2013
First published
27 Mar 2013

Dalton Trans., 2013,42, 9263-9273

Chiral and achiral (imino)phenoxy-based cationic group 4 non-metallocene complexes as catalysts for polymerization of renewable α-methylene-γ-butyrolactones

R. R. Gowda and E. Y.-X. Chen, Dalton Trans., 2013, 42, 9263 DOI: 10.1039/C3DT50430A

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