Organonickel compounds catalysts

The smoke characteristics of three types of pyrolants, namely nitropolymer pyrolants composed of NC-NG with and without a nickel catalyst, and a B-KNO3 pyrolant, have been examined in relation to the use of these pyrolants as igniters of rocket motors. Though nitropolymer pyrolants are fundamentally smokeless in nature, a large amount of black smoke is formed when they burn at low pressures below about 4 MPa due to incomplete combustion. Metallic nickel or organonickel compounds are known to catalyze the gas-phase reaction of nitropolymer pyrolants. 

Almost 60-70% of chemicals are produced by catalytic reactions, and 10-15% of the catalysts in catalytic reactions are homogeneous catalysts. Among the homogeneous catalysts, cobalt catalysts are mainly used for hydroformylation reactions, and next to cobalt, nickel catalysts are used for many others. The organonickel compounds are used not only as catalysts in industrial production but also for organic synthesis in laboratories. 

As in COMC (1982) and COMC (1995), catalysis results are only mentioned in those cases where rt-bonded organometallic complexes have been isolated or characterized. However, since the discovery of the a-diimine nickel catalysts in 1996, the interest in the field has been strongly polarized toward the study of the new olefin polymerization and oligomerization catalysts, many of them cr-organonickel compounds themselves. In order to account for this important aspect of the chemistry of (j-bonded organonickel compounds, the different kinds of catalysts and mechanistic studies are discussed in Section 8.02.3.4.4. 

Kawata, N., Mizireki, X, and Ozaki, A., Supported organonickel compounds as catalysts of alkenes oligomerization, J. Mol. Catal, 1, 275, 1975/1976. 

The proposed mechanism involves an initial transmetallation of the dialkyl (or diphenyl) zinc with Ni(acac)2 that generates an organonickel species. The latter then achieves the carbonickelation of the alkyne leading to an alkenylnickel(II) complex. Transmetallation with RZn(acac) then regenerates the Ni11 catalyst and affords the a-arylalkenylzinc compound (equation 32)46,47. 

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