Oligomerisation reactions

Titanium alkoxide complexes in the presence of triethylaluminium as activator have been reported as selective catalyst systems for the dimer-isation of ethylene to 1-butene with a selectivity higher than 99% towards 1-butene. It was observed that the bulkier the substituent at the ortho position, the lower the catalytic activity of the complex compared to 

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The complexity of the HCN oligomerisation reaction was also studied by Schwartz et al. (1984) in Nijmegen. The reactions worked best at a pH value which lies near the pK value of HCN. A list of the products of oligomerisation includes 38 compounds, including orotic acid, adenine, guanine and glycine, as well as more complex molecules such as isoleucine, glutamic acid, diaminosuccinic acid and... 

Figure 9.3 pictures the oligomerisation reaction Ni is an abbreviation for the nickel-ligand moiety, kg stands for the rate of the growth reaction, and kt for the rate of the termination reaction. These rate constants are the same for all intermediate nickel alkyls, except perhaps for the first two or three members of the sequence owing to electronic and steric effects. Interestingly, a simple kinetic derivation leads to an expression for the product distribution. One can... 

Another, highly selective oligomerisation reaction of ethene should be mentioned here, namely the trimerisation of ethene to give 1-hexene. Worldwide it is produced in a 0.5 Mt/y quantity and used as a comonomer for ethene polymerisation. The largest producer is BP with 40 % market share utilizing the Amoco process, formerly the Albemarle (Ethyl Corporation) process. About 25 % is made by Sasol in South Africa where it is distilled from the broad mixture of hydrocarbons obtained via the Fischer-Tropsch process, the conversion of syn-gas to fuel. The third important process has been developed by Phillips. 

Fig. 21 summarizes the complexes obtained. The formation of cycloadducts XIV can be explained formally as insertion into the Fe-N bond. By analogy to the well known cyclo-oligomerisation reactions of acetylenes94 in the presence of transition metals, it seems probable that the reaction occurs stepwise and is initiated by formation of a 7r-complex of the alkyne. The necessary vacant coordination site may be formed by loss of CO or by opening of one Fe-N bond. 

Summaries on dimerisation and oligomerisation reactions in ionic liquids have been published previously.[3,4] Predominantly complexes of either palladium or nickel have been employed in ionic liquids for dimerisation/oligomerisation reactions, but there are also examples where iron,[5] tungsten1 and rhodium17 have been used. Apart from metal catalysed dimerisation/oligomerisation reactions in ionic liquids, examples of electrochemical dimerisation have been reported, which include arylhalidcs17 and 3-(4-fluorophenyl) tluophcnc1 as substrates. 

Many useful, higher-molecular-weight fluoroalkenes can be conveniently prepared by fluoride-ion-induced oligomerisation reactions of smaller fluoroalkenes such as tetrafluoroethene and hexafluoropropene, and these methods are discussed in Section C. 

Note that this hypothesis is strongly supported by the oligomerisation reactions reported in Scheme 7. 

Analysis of the monomer fraction product of an oligomerisation reaction has been considered as a route to understanding the reaction mechanism [18, 26, 27]. 

Although alumina is lost from the zeolite framework, this loss is not always accompanied by a serious loss of activity. This can partly be explained by the formation of very strong acid sites during dealumination, but more likely this is caused by the high rate of the C-C bond formation and scission reactions on the acid sites. The cracking-oligomerisation reactions, which are much faster than dehydrocyclisation, quickly establish a pseudo-equilibrium hydrocarbon mixture that is independent of the size of the... 

Palladium compounds are also useful catalysts for oligomerisation and co-oligomerisation reactions. Dimerisation or co-dimerisation of olefins catalysed by palladium(n) chloride or, better, PdCl2(C6H5CN)2 involves a palladium(ii)-hydride intermediate as the catalytically active species. A similar reaction to dimerisation is coupling, e.g. of benzene to give biphenyl, which is also catalysed by palladium(ii) chloride and proceeds via palladium-phenyl u-bonded species. The nature of intermediates in... 

Carbon-carbon bond formation plays an essential role in chemical syntheses. In this regard, the development of transition metal-catalysed C-C bond-forming reactions has attracted much interest in recent years and titanium complexes have been found to be highly effective as catalysts for cross-couplings, hydroaminoallq lations, Barbier-type reactions and oligomerisation reactions. 

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