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Activation of Aryl and Heteroaryl Halides by an Iron(I) Complex Generated in the Reduction of [Fe(acac) 3 ] by PhMgBr: Electron Transfer versus Oxidative Addition
Author(s) -
Lefèvre Guillaume,
Jutand Anny
Publication year - 2014
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/chem.201304716
Subject(s) - chemistry , aryl , cyclic voltammetry , oxidative addition , medicinal chemistry , halide , reductive elimination , aryl halide , halogen , transmetalation , photochemistry , catalysis , inorganic chemistry , organic chemistry , electrochemistry , alkyl , electrode
The mechanism of the reactions of aryl/heteroaryl halides with aryl Grignard reagents catalyzed by [Fe III (acac) 3 ] (acac=acetylacetonate) has been investigated. It is shown that in the presence of excess PhMgBr, [Fe III (acac) 3 ] affords two reduced complexes: [PhFe II (acac)(thf) n ] ( n =1 or 2) (characterized by 1 H NMR and cyclic voltammetry) and [PhFe I (acac)(thf)] − (characterized by cyclic voltammetry, 1 H NMR, EPR and DFT). Whereas [PhFe II (acac)(thf) n ] does not react with any of the investigated aryl or heteroaryl halides, the Fe I complex [PhFe I (acac)(thf)] − reacts with ArX (Ar=Ph, 4‐tolyl; X=I, Br) through an inner‐sphere monoelectronic reduction (promoted by halogen bonding) to afford the corresponding arene ArH together with the Grignard homocoupling product PhPh. In contrast, [PhFe I (acac)(thf)] − reacts with a heteroaryl chloride (2‐chloropyridine) to afford the cross‐coupling product (2‐phenylpyridine) through an oxidative addition/reductive elimination sequence. The mechanism of the reaction of [PhFe I (acac)(thf)] − with the aryl and heteroaryl halides has been explored on the basis of DFT calculations.