Coordination Copolymerization of Severely Encumbered Isoalkenes with Ethylene:  Enhanced Enchainment Mediated by Binuclear Catalysts and Cocatalysts

• Published in: Journal of the American Chemical Society Vol. 127; no. 42; pp. 14756 - 14768
• Main Authors: Li, Hongbo, Li, Liting, Schwartz, David J, Metz, Matthew V, Marks, Tobin J, Liable-Sands, Louise, Rheingold, Arnold L
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 26.10.2005; Amer Chemical Soc
• Subjects: Alkenes - chemical synthesis; Alkenes - chemistry; Applied sciences; Carbon Isotopes; Catalysis; Chemistry; Chemistry, Multidisciplinary; Copolymerization; Crystallography, X-Ray; Ethylenes - chemistry; Exact sciences and technology; Magnetic Resonance Spectroscopy; Metals, Heavy - chemistry; Models, Molecular; Molecular Structure; Organic polymers; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Physical Sciences; Physicochemistry of polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Science & Technology; ASYMMETRIC CATALYSIS; OLEFIN POLYMERIZATION CATALYSTS; CONSTRAINED GEOMETRY CATALYSTS; THERMODYNAMIC STABILITY; ADDITION POLYMERIZATION; PROPYLENE POLYMERIZATION; METALLOCENIUM ION-PAIRS; METAL-ALKYL; AMINE ELIMINATION; COMONOMER ENCHAINMENT; Titanium Organic compounds; Ethylene; Reaction mechanism; NMR spectrometry; Transition metal Complexes; Kinetic parameter; Complex catalyst; Rate constant; Catalyst activity; Complex catalyst copolymerization; Ring opening copolymerization; Carbon 13
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja052995x

This contribution describes the implementation of the binuclear organotitanium “constrained geometry catalysts” (CGCs), (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](TiMe2)}2[EBICGC(TiMe2)2; Ti 2 ] and (μ-CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](TiMe2)}2[MBICGC(TiMe2)2; C1 − Ti 2 ], in combination with the bifunctional bisborane activator 1,4-(C6F5)2BC6F4B(C6F5)2 (BN 2 ) in ethylene + olefin copolymerization processes. Specifically examined are the classically poorly responsive 1,1-disubstituted comonomers, methylenecyclopentane (C), methylenecyclohexane (D), 1,1,2-trisubstituted 2-methyl-2-butene (E), and isobutene (F). For the first three comonomers, this represents the first report of their incorporation into a polyethylene backbone via a coordination polymerization process. C and D are incorporated via a ring-unopened pathway, and E is incorporated via a novel pathway involving 2-methyl-1-butene enchainment in the copolymer backbone. In ethylene copolymerization, Ti 2 + BN 2 enchains ∼2.5 times more C, ∼2.5 times more D, and ∼2.3 times more E than the mononuclear catalyst analogue [1-Me2Si(3-ethylindenyl)( t BuN)]TiMe2 (Ti 1 ) + B(C6F5)3 (BN) under identical polymerization conditions. Polar solvents are found to weaken the catalyst−cocatalyst ion pairing, thus influencing the comonomer enchainment selectivity.