Topic
Norbornene
About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.
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TL;DR: In this article, the authors used nickel(II) salicylaldiminato complexes [κ2-N,O-6-C(H)N(2,6-R2C6H3)-2,4-R‘2C 6H2O}NiMe(pyridine) to obtain high molecular weight copolymers (Mn > 104 g mol-1).
Abstract: Ethylene/norbornene and ethylene/1-butene copolymerization with nickel(II) salicylaldiminato complexes [{κ2-N,O-6-C(H)N(2,6-R2C6H3)-2,4-R‘2C6H2O}NiMe(pyridine)] (1a, R = 3,5-Me2C6H3, R‘ = I; 1b, R,R‘ = 3,5-(F3C)2C6H3; 1c, R = 3,5-(F3C)2C6H3, R‘ = I; 2, R = iPr, R‘ = I) were studied in toluene as a reaction medium and in emulsion, the latter affording polymer dispersions. High molecular weight copolymers (Mn > 104 g mol-1) are formed. Incorporation of ethylene is much preferred over butene incorporation, XBu/xBu ∼0.05 under typical reaction conditions, by comparison incorporation of the strained olefin norbornene is higher, XNB/xNB ∼0.25 (X = comonomer mole fraction in polymer; x = comonomer mole fraction in reaction mixture). Dispersions contained copolymers with up to 6 mol % comonomer (12 wt % for 1-butene; 20 wt % for norbornene). Incorporation of a few mol % of norbornene strongly decreases polymer crystallinity, which enhances the film forming properties of dispersions. Microstructure analysis by 13C...
63 citations
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TL;DR: Insight is provided into mechanistic details for the activation of a diatomic molecule by a prototypical FLP by the reversible formation of a [B]-NO complex intermediate followed by a slower isomerization-ring closure step to the cyclic aminoxyl radical.
Abstract: Described is a kinetics and computational study of the reaction of NO with the intramolecular bridged P/B frustrated Lewis pair (FLP) endo-2-(dimesitylphosphino)-exo-3-bis(pentafluorophenyl)boryl-norbornane to give a persistent FLP-NO aminoxyl radical. This reaction follows a second-order rate law, first-order in [FLP] and first-order in [NO], and is markedly faster in toluene than in dichloromethane. By contrast, the NO oxidation of the phosphine base 2-(dimesitylphosphino)norbornene to the corresponding phosphine oxide follows a third-order rate law, first-order in [phosphine] and second-order in [NO]. Formation of the FLP-NO radical in toluene occurs with a ΔH(‡) of 13 kcal mol(-1), a feature that conflicts with the computation-based conclusion that NO addition to a properly oriented B/P pair should be nearly barrierless. Since the calculations show the B/P pair in the most stable solution structure of this FLP to have an unfavorable orientation for concerted reaction, the observed barrier is rationalized in terms of the reversible formation of a [B]-NO complex intermediate followed by a slower isomerization-ring closure step to the cyclic aminoxyl radical. This combined kinetics/theoretical study for the first time provides insight into mechanistic details for the activation of a diatomic molecule by a prototypical FLP.
63 citations
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TL;DR: In this paper, the synthesis, characterization, and polymerization behaviors of iron, cobalt, chromium, copper and zinc complexes (3-7b) bearing chelating bulky 2,6-bis[1-(2,6)-diisopropylphenylimino)ethyl]pyridine ligand (1) or 2, 6-bis [1-( 2,5-ditertbutylphenymylnylnynylimin)ethyl pyridineligand (2) are reported.
Abstract: The syntheses, characterization, and ethylene and norbornene polymerization behaviors of iron, cobalt, chromium, copper and zinc complexes (3–7b) bearing chelating bulky 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine ligand (1) or 2,6-bis[1-(2,5-ditertbutylphenylimino)ethyl]pyridine ligand (2) are reported. X-ray diffraction study of the cobalt complex (4) shows the geometry of the cobalt center to be distorted trigonal bipyramid. Treatment of the iron, cobalt 2,6-bis[1-(2,5-ditertbutylphenylimino)ethyl pyridine complexes (3 and 4) with methylaluminoxane (MAO) lead to a highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE), while the corresponding chromium complex (5) is disclosed as moderate catalytic activity for the polymerization of ethylene. The specific catalytic activities were evaluated at different temperature and Al/M (M = Fe, Co and Cr) ratio. In addition, the complexes 3–5 and corresponding compounds of FeCl2, CoCl2(THF)1.5 and CrCl3(THF)3 can also catalyze vinyl polymerization of norbornene activated with MAO and show good activities. However, the copper and zinc complexes (6a–7b) showed no active in ethylene and norbornene polymerization in the presence of MAO.
63 citations
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TL;DR: Aryl cyanides add to norbornene and norbornadiene under nickel catalysis to give (2R*,3S*)-3-aryl-2-cyanobicyclo[2.2.1]heptanes and 3-aryl 2.5-cycles in good yields.
Abstract: Aryl cyanides add to norbornene and norbornadiene under nickel catalysis to give (2R*,3S*)-3-aryl-2-cyanobicyclo[2.2.1]heptanes and (2R*,3S*)-3-aryl-2-cyanobicyclo[2.2.1]hept-5-enes in good yields ...
62 citations
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TL;DR: In this article, five vanadium(III) complexes have been synthesized and characterized, in the presence of ethyl trichloroacetate (ETA) as a promoter, which are highly active precatalysts for ethylene polymerization and produce high molecular weight and linear polymers.
Abstract: Five novel vanadium(III) complexes [PhN = C(R-2)CHC(R-1)O]VCl2(THF)(2) (4a: R-1 = Ph, R-2 = CF3; 4b: R-1 =t-Bu, R-2 = CF3; 4c: R-1 = CF3, R-2 = CH3; 4d: R-1 = Ph, R-2 = CH3; 4e: R-1 = Ph, R-2 = H) have been synthesized and characterized. On activation with Et2AlCl, all the complexes, in the presence of ethyl trichloroacetate (ETA) as a promoter, are highly active precatalysts for ethylene polymerization, and produce high molecular weight and linear polymers. Catalyst activities more than 16.8 kg PE/mmolv h bar and weight-average molecular weights higher than 173 kg/ mol were observed under mild conditions.
62 citations