Naked-nickel catalysts

The formation of CDT is suppressed if ethylene as well as butadiene is brought into contact with a naked-nickel catalyst. Depending on the reaction conditions, the product is a mixture of m,tram-1,5-cyclodecadiene (CDD) and 1,tram-4,9-decatriene (DT) (90). With equal concentration of butadiene and ethylene the co-oligomerization occurs some six times faster than the cyclotrimerization of butadiene to CDT. 

Dependence of Product Distribution on C2H4 C4H6°, Using Naked -Nickel Catalyst at 39°-41°C... 

A reasonable mechanism for the co-oligomerization of butadiene with ethylene on a naked-nickel catalyst is shown in Eq. (49). Interaction of an ethylene molecule with the bis(7r-allyl) C8 chain produces a C,0 chain, containing both an alkyl- and a 7r-allylnickel group (XLVI). Coupling of the alkyl bond with the terminal atom of a m-Tr-allyl group or the terminal... 

Ligands with good acceptor character (e.g., triphenylphosphite, Table IX) stabilize the m-7r-allyl, cr-alkyl intermediate (XLVIb) and only CDD is formed. The stabilization introduced by triphenylphosphite is so effective that even at elevated temperatures (60° C) practically no DT results, while a naked-nickel catalyst at the same temperature produces DT and CDD in about equal proportions. 

I. Butadiene Styrene = 2 1 20 C in autoclave, naked-nickel catalyst. 

A parallel may be drawn between the formation of CDD and DT from ethylene and butadiene using a naked-nickel catalyst and the formation of trialkylamine and octatriene. In both cases low temperature favors the formation of a C—C or C—N bond (i.e., formation of CDD or R3N), whereas at higher temperatures (< 60°) the hydrogen-transfer reaction becomes predominant (i.e., formation of DT and w-octatriene). 

The result of the reaction with MCP and dimethyl bicyclo[2.2.1]hept-2-ene-2,3-dicarboxylate vide supra) is in contrast to the outcome of most nickel-catalyzed [3 + 2] cycloadditions in the absence of phosphanes ( naked nickel catalysts) which employ unsaturated esters as cosubstrates. Normally, products arising from formal proximal cleavage of the three-membcred ring are formed in these cases. All of these reactions proceed readily at slightly above room temperature (20 40°C) and are highly regio- and stereoselective. 

With (l-methylethylidene)cyclopropane (1) and a naked nickel catalyst, cyclodimers are formed with methyl acrylate in a combined yield of 59% and an isomeric ratio (2/3) of 96 4. When the reaction is performed in the presence of tris(2-phenylphenyl) phosphite as modifying ligand, the combined yield increases to 89% but the selectivity drops to 85 15. ... 

Fig. 4.11 Effect of 1-decene concentration on poly(norbornene) MW (naked nickel catalyst).

Fig. 4.15 Reactive end-groups formed via chain transfer to olefinic monomers using the naked nickel catalyst.

Fig. 4.1G The direct synthesis of A-B block copolymers using the naked nickel catalyst with polymeric chain transfer agents.

Subjects specifically excluded are cycloolefin polymerizations catalyzed by naked nickel catalysts, palladium-catalyzed ethylene/carbon monoxide alternating copolymerizations, metathesis polymerizations of cyclic olefins, and diene polymerizations... 

Fig. 12.5 Catalytic conversion of 1,3-butadiene into 1,5,9-cyclododecatriene using a naked nickel catalyst.

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