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

Organotransition metal chemistry
o o
Il 11
RCNHR" RCOR" RCHO
o ~"· IR"O" ~ACOR'
11
1
~ Bu SnH
RCX+tPdL'2--- L2Pd(COR}XJ
3
RCHO
[co
R'M
---+R-R'
Fig. 7.4 Summary ofreactions catalysed by palladium complexes. R,R' = e.g. aryl, vinyl,
benzyl, heteroaromatic, allyl.
(c) CARBONYLATION REACTIONS. The organopalladium species L 2 PdRX form
acyl intermediates L 2 Pd(COR)X with carbon monoxide. These react with alcohols
to form esters, while amines afford amides. They are also cleaved by hydrogen
yielding aldehydes. All these conversions take place catalytically. They are
summarized in Fig. 7.4.
7.1.8 Some alkyl derivatives of cobalt. Vitamin B 12 coenzyme and
the cobaloximes.
Octahedral complexes of cobalt(III) (d 6 ) are generally diamagnetic 18-electron
compounds which are kinetically inert to substitution. This applies to the group of
organometallic compounds which includes Vitamin B 12 coenzyme, a rare
example of a natural product which contains a metal-carbon bond. The human
body contains 2-5 mg, mostly in the liver. The coenzyme is implicated in a whole
range of biochemical processes of the general type
X H H X
1 1 1 1
-c-c-~-c -c- X=e.g. NH,, C(=CH 2 )CO;, CH(NH,)CO;
1 1 1 1
in which two groups X and H on adjacent carbon atoms are exchanged. This
exchange may be followed by elimination of XH, in which case the process is
irreversible.
230
X H H X H
1 1 1 1 1 -?0
-C-C-OH -----+-C-C-OH -----+-C-C + XH (X= OH, NH 2 )
1 1 1 1 1