1,5,9-Cyclododecatriene catalysts, nickel complexes

Among transition metal complexes used as catalysts for reactions of the above-mentioned types b and c, the most versatile are nickel complexes. The characteristic reactions of butadiene catalyzed by nickel complexes are cyclizations. Formations of 1,5-cyclooctadiene (COD) (1) and 1,5,9-cyclododecatriene (CDT) (2) are typical reactions (2-9). In addition, other cyclic compounds (3-6) shown below are formed by nickel catalysts. Considerable selectivity to form one of these cyclic oligomers as a main product by modification of the catalytic species with different phosphine or phosphite as ligands has been observed (3, 4). 

Homogeneous nickel complexes proved to be versatile catalysts in dimerization and trimerization of dienes to yield different oligomeric products.46-55 Depending on the actual catalyst structure, nickel catalyzes the dimerization of 1,3-butadiene to yield isomeric octatrienes, and the cyclodimerization and cyclotrimerization to give 1,5-cyclooctadiene and all-trans-l,5,9-cyclododecatriene, respectively46 56 [Eq. (13.13)]. Ziegler-type complexes may be used to form cis,trans,trans-1,5,9-cyclododecatriene37,57 58 [Eq. (13.14)], which is an industrial intermediate ... 

Nickel-triarylphosphite complexes catalyze the dimerisation of butadiene to cyclooctadiene. Cyclododecatriene is an unwanted by-product, which results from trimerization catalyzed by the same catalyst. Table 3.2 shows the product yields using various ligand-metal complexes (the remainder in each case is a tarry polymeric material). 

Two isomeric 1,5,9-cyclododecatrienes, namely, trans,trans,cis-CijH 18 (XLVI) and trans,trans,trans-CuHis (XLVII), are formed in good yield by the cyclic trimerization of butadiene using certain Ziegler-type catalysts 247, 250, 251, 252). The formation of these 12-membered ring hydrocarbons probably proceeds via metal 7r-complexed intermediates. When the cyclic triene (XLVII) is treated with nickel acetylacetonate and... 

What compounds are the active catalysts in this process By this method of catalyst preparation we do not obtain a mixture of indefinite composition, but TT-complexes which can be isolated and are mostly crystalline. If, for instance, nickel acetylacetonate is reduced in the presence of P(CeH5)3 we obtain a new compound, Ni-(0)-[P(CeH5)3]4. This compound is itself an active catalyst for the cyclo-oligomerization of butadiene, producing about 65 to 70% cyclo-octadiene, 20% vinylcyclohexene, and 10% cyclododecatriene. Instead of P(CeH5)3 we can introduce As(CeH5)3 and isolate Ni-(0)-[As(CeH5)3]4 as an active cata-... 

The next step was to investigate the reaction of the centro-nickel compound wdth butadiene. When a solution of this compound is saturated with butadiene at room temperature, we observe that after a certain period the excess of butadiene has reacted with formation of cyclododecatriene and a new complex which can be isolated by removing the cyclododecatriene under high vacuum. The same catalytic reaction can be carried out by using bis (1,5-cyclo-octadiene) nickel as a catalyst. Cyclododecatriene synthesized in this way consists of three isomers. The main product is trans,trans,trans-cyc ododecdAx ene and the isolated by-products are transytrans,cis- and cis,cis,trans-cyc ododec3itnene. The latter compound is a new isomer, previously imknown (b.p.14 110° C., 1.5129). The synthesis of... 

Butadiene reacts with cyclododecatriene-nickel or bis(cyclooctadiene)-nickel at 20° C, replacing the olefinic ligands and forming a new molecule of cyclododecatriene (99), In this reaction atomic nickel must be the catalyst, as it is in some reactions of bis(acrylonitrile)-nickel. Most of the catalytically formed cyclododecatriene has the trans-trans-cis configuration, but, small amounts of the trans-cis-cis isomer have also been detected. When the reaction between (LIV) and butadiene was carried out at — 40°C. Wilke et al. were able to isolate an intermediate (LVI) the nature of which was of great importance in elucidating reaction mechanism. Complex (LVI) is actually a bis(7r-allyl)-nickel type of compound involving a twelve-carbon-atom chain, formed by condensation of three molecules of butadiene. Ally ... 

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