Handbook of Functionalized Organometallics Applications in S

15.3 Electrochemical Synthesis
and distilled before use though a quite high dryness is not required. A low concentration
(0.01±0.02 M) of tetrabutylammonium salt, bromide, iodide or tetrafluoroborate,
is added to the medium to ensure a good initial conductivity. However
if the electrolysis is conducted in the presence of Zn(II) (either ZnBr 2 or
ZnCl 2) added to the medium the ammonium salt is unnecessary. Electrolyzes are
usually conducted under argon at 0±60 C under constant current density of 0.5±
5 A/dm 2 of cathode. Under these reaction conditions current electrolyzes allows
preparation of 1±15 millimoles of product.
DC POWER SUPPLY
_
+
Cathode
Fig.15.1 Electrochemical cell used at laboratory scale for
electrosynthesis of zinc reagents and C±C bond.
15.3
Electrochemical Synthesis Involving Functionalized Organo-Cobalt
or -Iron Intermediates Derivatives
15.3.1
Introduction
Sacrificial anode (Mg, Zn, Fe)
Stirring bar
Output of inert gas
Cooling or heating bath
Electrochemical cross-coupling reaction from functionalized organic halides
requires generally catalytic amounts of a transition metal. This transition metal is
most often nickel. The success of these reactions is due to the formation and the
reactivity of an organometallic intermediate formed in situ by electrochemistry. To
the best of our knowledge, these compounds have not been yet isolated and characterized.
For example, the compounds ArNi II XorAr 2Ni and even ArNi I resulting from
the electroreduction of ArNiX [16], are assumed to arise in the cross-coupling be-
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