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

IF 2.9 3区 化学 Q2 CHEMISTRY, INORGANIC & NUCLEAR
Clement G. Collins Rice, Justin A. Hayden, Adam D. Hawkins, Louis J. Morris, Zoë R. Turner, Jean-Charles Buffet and Dermot O’Hare*, 
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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.

Abstract Image

Abstract Image

过渡金属二甲基茚基苯氧基(PHENI*)络合物的结构和乙烯聚合反应趋势
合成并表征了一系列全甲基茚基苯氧基(PHENI*)过渡金属氯化物配合物(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)。辅助氯配体很容易与卤化物、烷基、烷氧基、芳氧基或酰胺交换,形成 PHENI* 复合物 [L]TiX2 (8-17;X = Br、I、Me、CH2SiMe3、CH2Ph、NMe2、OEt、ODipp)。这些 PHENI* 复合物的固态晶体结构表明,两种构象中的一种可能更受青睐,其参数是特征扭转角(TA′),在这种构象中,η5 系统要么远离金属中心,要么朝向金属中心。与茚基 PHENICS 复合物相比,过甲基茚基(I*)配体似乎更倾向于金属中心更易接近的构象。当在固体聚甲基铝氧烷(sMAO)上进行异质化时,钛 PHENI* 复合物对乙烯的聚合表现出卓越的催化活性。与同类 PHENICS 催化剂相比,钛 PHENI* 复合物具有更高的催化活性,同时还能生成超高分子量聚乙烯 (UHMWPE)。在阳离子化实验中观察到了催化剂-催化剂离子配对效应,并发现这种效应在均相催化体系中非常显著;这些效应还与辅助配体离去基团在浆料相聚合中的影响有关。催化效率和聚乙烯分子量随压力的增加而增加,PHENI* 催化剂在超高分子量聚乙烯的受控合成中属于最活跃的催化剂。
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来源期刊
Organometallics
Organometallics 化学-无机化学与核化学
CiteScore
5.60
自引率
7.10%
发文量
382
审稿时长
1.7 months
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.
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