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Mechanism of the Electrochemical Conversion of Aryl Halides to Arylzinc Compounds by Cobalt Catalysis in DMF/Pyridine
Author(s) -
Seka Sylvaine,
Buriez Olivier,
Nédélec JeanYves,
Périchon Jacques
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020603)8:11<2534::aid-chem2534>3.0.co;2-s
Subject(s) - bromide , cobalt , catalysis , halide , chemistry , pyridine , aryl , transmetalation , dimethylformamide , zinc , disproportionation , inorganic chemistry , oxidative addition , electrochemistry , catalytic cycle , organic chemistry , alkyl , solvent , electrode
The study of the electrochemical behavior of cobalt bromide, CoBr 2 , in the presence of zinc bromide, ZnBr 2 , and aryl halides, ArX, in a dimethylformamide (DMF)/pyridine (9:1, v / v ) mixture allowed us to complete the study of the mechanism of the electrochemical conversion of aryl halides into arylzinc compounds by using cobalt catalysis. The last step of the catalytic process has been shown to be a transmetalation reaction between the arylcobalt( II ) species and zinc ions that regenerates the cobalt( II ) catalyst. The effect of zinc bromide on each step of the catalytic cycle has been studied. It is especially shown that the presence of ZnBr 2 stabilizes the electrogenerated Co I but has no effect on the rate constant of the oxidative addition of aryl halides, ArX, to Co I . Rate constants for the disproportionation reaction of Co I and the oxidative addition have been determined in the presence of ZnBr 2 and compared with the values obtained in its absence.