Nickel-complex-catalyzed reactions telomerization

These telomerization reactions of butadiene with nucleophiles are also catalyzed by nickel complexes. For example, amines (18-23), active methylene compounds (23, 24), alcohols (25, 26), and phenol (27) react with butadiene. However, the selectivity and catalytic activity of nickel catalysts are lower than those of palladium catalysts. In addition, a mixture of monomeric and dimeric telomers is usually formed with nickel catalysts ... 

In homogeneous catalysis telomerization is defined as the oligomerization of dienes with incorporation of a nucleophile. For example, two molecules of butadiene react with one nucleophile HY to form telomers. This reaction is catalyzed by various organometallic compounds of the transition metals, especially by palladium and nickel complexes. 

The linear telomerization reaction of dienes was one of the very first processes catalyzed by water soluble phosphine complexes in aqueous media [7,8]. The reaction itself is the dimerization of a diene coupled with a simultaneous nucleophilic addition of HX (water, alcohols, amines, carboxylic acids, active methylene compounds, etc.) (Scheme 7.3). It is catalyzed by nickel- and palladium complexes of which palladium catalysts are substantially more active. In organic solutions [Pd(OAc)2] + PPhs gives the simplest catalyst combination and Ni/IPPTS and Pd/TPPTS were suggested for mnning the telomerizations in aqueous/organic biphasic systems [7]. An aqueous solvent would seem a straightforward choice for telomerization of dienes with water (the so-called hydrodimerization). In fact, the possibility of separation of the products and the catalyst without a need for distillation is a more important reason in this case, too. 

Solutions of the nickel(O) and palladium(O) complexes of 1,3,5-triaza-7-phosphaadamantane, PTA (82) and tris(hydroxymethyl)phosphine (98) in water catalyze the oligomerization and telomerization of 1,3-butadiene at 80 °C. Although high yields and good selectivities to octadienyl products (87 %) were obtained, the complexes (or the intermediate species formed in the reaction) dissolve sufficiently in the organic phase ofthe monomer and the products to cause substantial metal leaching [17],... 

The telomerization reaction is catalyzed by various transition metal complexes as nickel, palladium or platinum, but among them, palladium catalysts proved to be the most efficient. With palladium catalysts, linear cis, trans and branched octadienyl ethers are the major products and side products that can arise from the linear dimerization or the degenerative telomerization of butadiene are formed in marginal amounts (Scheme 6). 

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