Alkene oligomerization ethylene

Boratabenzene complexes of Group 3 and Group 6 metals serve as effective catalysts for the oligomerization/polymerization of ethylene. For example, [(C5H5B-Ph)2ScPh]2, pretreated with H2, oligomerizes ethylene to furnish 1-alkenes.17a In the case of a Cr(III)-boratabenzene complex, ethylene is polymerized to afford... 

The production of 1-alkenes from ethylene oligomerization was carried out with high selectivity in ionic liquids in the presence of a cationic nickel complex catalyst (ri -methallyl)-[bis(diphenylphosphino)methane-monoxide-K -P,0]nickel(II) hexafluoroantimonate, [(mall)-Ni(dppmo)]Sbp6 (240). The overall reaction rate of... 

The simplest possible alkene oligomerization reaction, the dimerization of ethylene to butenes, is a well-studied reaction, and an industrial process was also developed for the selective formation of 1-butene42 (IFP Alphabutol process). 

Ethylene oligomerization is a homogeneous catalyzed reaction that converts ethylene into 1-alkenes. Commercial ethylene oligomerization processes are catalyzed by AI-, Ti, Zr-, Ni-, and Cr-complexes. 1-Alkenes find major industrial applications as co-monomers in polyethylene manufacturing or as intermediates for the production of plasticizer alcohols, detergents, or lubricants. 

Ans Ethylene a-alkenes (oligomerization), acetaldehyde (oxidation) propylene n-butyraldehyde (hydroformylation), propylene oxide (epoxidation) CO acetic acid, acetic anhydride (carbonylation). 

As outlined earlier, this class of materials is the product of the Friedel-Crafts alkylation of benzene with a long-chain alkyl group the prime example is dodecyl-benzene. This compound may be derived from an alkyl chloride containing an average of 12 carbon atoms. The source of the alkyl chain may be a particular cut of petroleum distillate or a synthetic hydrocarbon chain obtained by the controlled oligomerization of a low-molecular-weight alkene—generally ethylene or propylene. 

The 7r-back donation stabilizes the alkene-metal 7c-bonding and therefore this is the reason why alkene complexes of the low-valent early transition metals so far isolated did not catalyze any polymerization. Some of them catalyze the oligomerization of olefins via metallocyclic mechanism [25,30,37-39]. For example, a zirconium-alkyl complex, CpZrn(CH2CH3)(7/4-butadiene)(dmpe) (dmpe = l,2-bis(dimethylphosphino)ethane) (24), catalyzed the selective dimerization of ethylene to 1-butene (Scheme I) [37, 38]. 

Alkenes. At present alkene isomerization is an important step in the production of detergent alkylates (Shell higher olefin process see Sections 12.3 and 13.1.3).264 265 Ethylene oligomerization in the presence of a nickel(O) catalyst yields terminal olefins with a broad distribution range. C4-C6 and C2o+ alkenes, which are not suitable for direct alkylate production, are isomerized and subsequently undergo metathesis. Isomerization is presumably carried out over a MgO catalyst. 

Another simple oligomerization is the dimerization of propylene. Because of the formation of a relatively less stable branched alkylaluminum intermediate, displacement reaction is more efficient than in the case of ethylene, resulting in almost exclusive formation of dimers. All possible C6 alkene isomers are formed with 2-methyl-1-pentene as the main product and only minor amounts of hexenes. Dimerization at lower temperature can be achieved with a number of transition-metal complexes, although selectivity to 2-methyl-1-pentene is lower. Nickel complexes, for example, when applied with aluminum alkyls and a Lewis acid (usually EtAlCl2), form catalysts that are active at slightly above room temperature. Selectivity can be affected by catalyst composition addition of phosphine ligands brings about an increase in the yield of 2,3-dimethylbutenes (mainly 2,3-dimethyl-1-butene). 

Variations of this mechanism included the suggestion of a partially bonded alkene molecule,299 the participation of a titanium-aluminum ion pair,300 and a concerted alkene insertion.301 The development of the activator-alkyl mechanism was probably strongly influenced by the Aufbau reaction, studied originally by Ziegle.102 He observed that Group I—III alkyl compounds such as Et3Al catalyzed the oligomerization of ethylene to terminal alkenes. Additional evidence of such mechanism comes from the fact that alkylaluminum compounds exist in dimeric... 

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