Clement G. Collins Rice, Justin A. Hayden, Adam D. Hawkins, Louis J. Morris, Zoë R. Turner, Jean-Charles Buffet and Dermot O’Hare*,
{"title":"Trends in Structure and Ethylene Polymerization Reactivity of Transition-Metal Permethylindenyl-phenoxy (PHENI*) Complexes","authors":"Clement G. Collins Rice, Justin A. Hayden, Adam D. Hawkins, Louis J. Morris, Zoë R. Turner, Jean-Charles Buffet and Dermot O’Hare*, ","doi":"10.1021/acs.organomet.3c00503","DOIUrl":null,"url":null,"abstract":"<p >A family of <i>ansa</i>-permethylindenyl-phenoxy (PHENI*) transition-metal chloride complexes has been synthesized and characterized (<b>1–7</b>; {(η<sup>5</sup>-C<sub>9</sub>Me<sub>6</sub>)Me(R″)Si(2-R-4-R′-C<sub>6</sub>H<sub>2</sub>O)}MCl<sub>2</sub>; R,R′ = Me, <sup><i>t</i></sup>Bu, Cumyl (CMe<sub>2</sub>Ph); R″ = Me, <sup><i>n</i></sup>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<sub>2</sub> (<b>8–17</b>; X = Br, I, Me, CH<sub>2</sub>SiMe<sub>3</sub>, CH<sub>2</sub>Ph, NMe<sub>2</sub>, 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<sup>5</sup> 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.</p>","PeriodicalId":56,"journal":{"name":"Organometallics","volume":"43 4","pages":"540–556"},"PeriodicalIF":2.9000,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.organomet.3c00503","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organometallics","FirstCategoryId":"92","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.organomet.3c00503","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
引用次数: 0
Abstract
A family of ansa-permethylindenyl-phenoxy (PHENI*) transition-metal chloride complexes has been synthesized and characterized (1–7; {(η5-C9Me6)Me(R″)Si(2-R-4-R′-C6H2O)}MCl2; R,R′ = Me, tBu, Cumyl (CMe2Ph); R″ = Me, nPr, 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]TiX2 (8–17; X = Br, I, Me, CH2SiMe3, CH2Ph, NMe2, 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 η5 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.
期刊介绍:
Organometallics is the flagship journal of organometallic chemistry and records progress in one of the most active fields of science, bridging organic and inorganic chemistry. The journal publishes Articles, Communications, Reviews, and Tutorials (instructional overviews) that depict research on the synthesis, structure, bonding, chemical reactivity, and reaction mechanisms for a variety of applications, including catalyst design and catalytic processes; main-group, transition-metal, and lanthanide and actinide metal chemistry; synthetic aspects of polymer science and materials science; and bioorganometallic chemistry.