University of Hull logo

Selective ethylene trimerization by titanium complexes bearing phenoxy-imine ligands: NMR and EPR Spectroscopic studies of the reaction intermediates

Soshnikov, Igor E.; Semikolenova, Nina V.; Ma, Jing; Zhao, Ke-Qing; Zakharov, Vladimir A.; Bryliakov, Konstantin P.; Redshaw, Carl; Zhao, Ke Qing; Talsi, Evgenii P.

Authors

Igor E. Soshnikov

Nina V. Semikolenova

Jing Ma

Ke-Qing Zhao

Vladimir A. Zakharov

Konstantin P. Bryliakov

Profile Image

Professor Carl Redshaw C.Redshaw@hull.ac.uk
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry

Ke Qing Zhao

Evgenii P. Talsi

Abstract

The catalyst systems (FI)TiCl₃/MAO (FI = phenoxyimine ligand with an additional aryl–O–CH₃ donor) display exceptionally high activity in selective ethylene trimerization. By means of NMR and EPR spectroscopy, the nature of the Ti species formed in the catalyst systems (FI)TiCl₃/MAO, (FI)TiCl₃/MMAO, and (FI)TiCl₃/AlR₃/[Ph₃C]⁺[B(C₆F₅)₄]⁻ (R = Me, Et, ⁱBu) has been studied. It was shown that outer-sphere ion pairs of the type [(FI)TiIVMe₂]⁺[A]⁻ ([A]− = [MeMAO]⁻, [MeMMAO]⁻, [B(C₆F₅)₄]⁻) are formed at the initial stage of the reaction of (FI)TiCl₃ with MAO, MMAO, and AlMe₃/[Ph₃C]⁺[B(C₆F₅)₄]⁻. These ion pairs further partially convert into TiIII and TiII species. In the systems (FI)TiCl₃/MAO and (FI)TiCl₃/AlMe₃/[Ph₃C]⁺[B(C₆F5)₄]⁻, complexes with the proposed structures (FI)TiIIIMe₂, (FI)TiIICl, and [(FI)TiII(S)]⁺[A]⁻ ([A]− = [MeMAO]⁻, [B(C₆F₅)4)]⁻, S = solvent, vacancy) were observed (concentrations of TiIII species was lower than those of the TiII congeners). In contrast, in the system (FI)TiCl₃/MMAO, the concentrations of TiIII species (ion pairs of the type [(FI)TiIII(μ-H)(μ-Cl)AlⁱBu₂]⁺[MeMMAO]⁻) were higher than those of the TiII counterparts (ion pairs [(FI)TiII(S)]⁺[MeMMAO]⁻). The system (FI)TiCl₃/MMAO displays lower activity and selectivity in 1-hexene formation, in comparison to (FI)TiCl₃/MAO, due to undesirable PE generation. Probably, TiII and TiIV ion pairs are those participating in ethylene trimerization.

Journal Article Type Article
Publication Date Mar 24, 2014
Journal Organometallics
Print ISSN 0276-7333
Electronic ISSN 1520-6041
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 33
Issue 6
Pages 1431-1439
Institution Citation Soshnikov, I. E., Semikolenova, N. V., Ma, J., Zhao, K., Zakharov, V. A., Bryliakov, K. P., …Talsi, E. P. (2014). Selective ethylene trimerization by titanium complexes bearing phenoxy-imine ligands: NMR and EPR Spectroscopic studies of the reaction intermediates. Organometallics, 33(6), 1431-1439. https://doi.org/10.1021/om500017r
DOI https://doi.org/10.1021/om500017r
Keywords Ethylene trimerization , NMR spectroscopy, EPR spectroscopy
Publisher URL http://pubs.acs.org/doi/abs/10.1021/om500017r
Copyright Statement ©2015 University of Hull
Additional Information This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/om500017r

Files



You might also like


Downloadable Citations