title: 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-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)OH] in toluene at -30 °C to 25 °C cleanly affords the corresponding achiral (imino)phenoxy-tribenzyl complexes, [(2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)O]Zr(Bn)3 (1) and [(2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)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=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-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)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-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)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.
authors.affiliation: Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA.
authors.forename: Ravikumar R
authors.initials: RR
authors.lastname: Gowda
authors.forename: Eugene Y-X
authors.initials: EY
authors.lastname: Chen
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D002412:Cations / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D058105:Polymerization; D013696:Temperature
chemical_list: D002412:Cations; D028581:Lanthanoid Series Elements; D009942:Organometallic Compounds; D015107:4-Butyrolactone