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

Catalysis of reactions of alkenes by transition metal complexes
NiL4 + H+ ~ HNiL+ 4 ~
(18) (18)
RCH~CHCH 3~
HNiL3(RCH=CHCH3)
(18)
HNiL\ + L
(16)
\RCH 2 CH~CH2
+
HNiL3(RCH 2 CH =CH2)
(18)
+
L3 NiCH 2 CH 2 CH 2 R
Fig. 12.1 Catalytic cycle for isomerization of a terminal alkene by a 1, 2-hydrogen shift.
The figures in parentheses (16 ), ( 18) indicate the electronic configuration ofthe
metal. r.d. =rate determining step.
(16)
RCH~CHCH 3 ~ F•(C0)
4
~ RCH 2 CH=CH2
(RCH=CHCH3)Fe(C0)4 (16)
/ (18)
COf (RCH 2 CH=CH2)Fe(C0) 4 (18)
(16) RCH=CHCH 3
L ~·
(C0) 3~~
Fe-H
(COJ 3
(18)
(RCH 2 CH=CH2 )Fe(C0) 3 (16)
~
Fig. 12.2 Catalytic cycle for isomerization of an alkene by a 1. 3-hydrogen shift.
that ali species have an independent existence. Sometimes two consecutive steps
could be linked by a synchronous process so that the species shown may represent
a transition state rather than an identifiable intermediate.
The second mechanism is followed, for example, by Fe 3 (C0) 11 • It involves an
1] 3 -allyl metal hydride (Fig. 12.2 ). The rate determining step is thought to be loss
of CO from the 18-electron species Fe(C0) 4 (alkene).
The 1] 3 -allyl mechanism probably operates also in alkene isomerizations
catalysed by bis(benzonitrile )dichloropalladium.
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