_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Catalysis of reactions of alkenes by transition metal complexes
commercial process, which has been in operation for about 15 years. occurs in
three stages.
(i) Formation of mononitriles
CH 3
~ +HNiL2CN- ~ ----+
NilmCN
(m=1,2)
NCCH2 CH = CHCH 3
3-pentenenitrile
+
H2C=CHCH(CH 3 JCN
2-methyl-3-butenenitrile
{ii) Isomerization of the branched mononitrile into the linear 3-pentenenitrile
using a similar NiL 4 ~NiL 3 system.
(iii) Hydrocyanation of 3-pentenenitrile.
~CN ~CN
2-pentenenitrile
(Thermodynamic product)
r
l
"'"'"
~cN-vcN
[Na [Ni]-H
/
4 -pentenenitrile
( kinetic product)
Adiponitrile
([Ni] means nickel + unspecified ligands)
3-Pentenenitrile is first rapidly isomerized by the nickel catalyst to 4-pentenenitrile.
Addition of hydrogen cyanide then affords adiponitrile as the major product.
This is fortunate, as the unwanted conjugated 2-pentenenitrile is thermodynamically
more stable than either the 3- or the 4-isomer. The favourable initial course
of the isomerization is thought to be controlled by the formation of a cyclic
intermediate or transition state in which the nitrile group coordinates to nickel.
12.3 .4 Dimerization of ethene
While investigating the oligomerization of ethene by aluminium alkyls (p. 80),
Ziegler and coworkers noticed that in the presence of traces of nickel dimerization
to 1-butene occurs instead. Very active catalysts can be generated by adding an
alkylaluminium halide to [ ('7 3 -C 3 H 5 )NiCIL. The phosphine complexes NiL 4 are
also effective in the presence of acids. A nickel hydrido complex is first formed
which adds to ethene to give an ethyl intermediate which can either eliminate 1-
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