Trends in Structure and Ethylene Polymerization Reactivity of Transition-Metal Permethylindenyl-phenoxy (PHENI*) Complexes.

Autor: Collins Rice CG; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., Hayden JA; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., Hawkins AD; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., Morris LJ; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., Turner ZR; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., Buffet JC; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K., O'Hare D; Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K.
Jazyk: angličtina
Zdroj: Organometallics [Organometallics] 2024 Feb 14; Vol. 43 (4), pp. 540-556. Date of Electronic Publication: 2024 Feb 14 (Print Publication: 2024).
DOI: 10.1021/acs.organomet.3c00503
Abstrakt: A family of ansa -permethylindenyl-phenoxy (PHENI*) transition-metal chloride complexes has been synthesized and characterized ( 1-7 ; {(η 5 -C 9 Me 6 )Me(R″)Si(2-R-4-R'-C 6 H 2 O)}MCl 2 ; R,R' = Me, t Bu, Cumyl (CMe 2 Ph); R″ = Me, n Pr, Ph; M = Ti, Zr, Hf). The ancillary chloride ligands could readily be exchanged with halides, alkyls, alkoxides, aryloxides, or amides to form PHENI* complexes [L]TiX 2 ( 8-17 ; X = Br, I, Me, CH 2 SiMe 3 , CH 2 Ph, NMe 2 , OEt, ODipp). The solid-state crystal structures of these PHENI* complexes indicate that one of two conformations may be preferred, parametrized by a characteristic torsion angle (TA'), in which the η 5 system is either disposed away from the metal center or toward it. Compared to indenyl PHENICS complexes, the permethylindenyl (I*) ligand appears to favor a conformation in which the metal center is more accessible. When heterogenized on solid polymethylaluminoxane (sMAO), titanium PHENI* complexes exhibit exceptional catalytic activity toward the polymerization of ethylene. Substantially greater activities are reported than for comparable PHENICS catalysts, along with the formation of ultrahigh-molecular-weight polyethylenes (UHMWPE). Catalyst-cocatalyst ion pairing effects are observed in cationization experiments and found to be significant in homogeneous catalytic regimes; these effects are also related to the influence of the ancillary ligand leaving groups in slurry-phase polymerizations. Catalytic efficiency and polyethylene molecular weight are found to increase with pressure, and PHENI* catalysts can be categorized as being among the most active for the controlled synthesis of UHMWPE.
Competing Interests: The authors declare no competing financial interest.
(© 2024 The Authors. Published by American Chemical Society.)
Databáze: MEDLINE
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