Alkyl groups, nickel-catalyzed addition

Butene. Commercial production of 1-butene, as well as the manufacture of other linear a-olefins with even carbon atom numbers, is based on the ethylene oligomerization reaction. The reaction can be catalyzed by triethyl aluminum at 180—280°C and 15—30 MPa ( 150 300 atm) pressure (6) or by nickel-based catalysts at 80—120°C and 7—15 MPa pressure (7—9). Another commercially developed method includes ethylene dimerization with the Ziegler dimerization catalysts, (OR) —AIR, where R represents small alkyl groups (10). In addition, several processes are used to manufacture 1-butene from mixed butylene streams in refineries (11) (see BuTYLENEs). 

Nickel catalyzed O-H additions to imsaturated systems are limited to the hydration reactions of nitriles for the synthesis of amides. These reactions have been widely studied by Prof. J. J. Garcia and his research group and their results recently reviewed [60]. They reported the isolation and characterization of Ni(0) complexes of type [(dippe)Ni(ri -NCR], R = aryl, heteroaryl or alkyl, derived from the reductive interaction of [(dippe)NiH]2 with organic cyanides. The catalytic and synthetic utility of these complexes was demonstrated first in the catalytic hydration of benzonitrile and acetonitrile [61] and then extended to dicyanobenzenes [62], to mono- and dicyanoalkanes [63] and finally to cyanopyridines [64]. 

Numerous complexes of nickel(II) and nickel(O) catalyze the addition of the Si-H bond to olefins. Among such catalysts are nickel-phosphine complexes, e.g., Ni(PR3)2X2 (where X=C1, I, NO3 R=alkyl and aryl), Ni(PPh3)4, and Ni-(CO)2(PPh3)2, as well as bidentate complexes of NiCl2-(chelate) and Ni(acac)2L (I phosphine), and Ni(cod)2(Pr3)2 [1-5]. A characteristic feature of nickel-phosphine-catalyzed olefin hydrosilylation is side reactions such as H/Cl, redistribution at silicon and the formation of substantial amounts of internal adducts in addition to terminal ones [69]. Phosphine complexes of nickel(O) and nickel(II) are used as catalysts in the hydrosilylation of olefins with functional groups, e.g., vinyl acetate, acrylonitrile [1-4], alkynes [70], and butadiynes [71]. 

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