Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (5): 852-858.doi: 10.3866/PKU.WHXB201503026


Reaction Mechanism for the Iron-Catalyzed Biaryl Cross-Coupling of Aryl Grignard Reagents

REN Qing-Hua, SHEN Xiao-Yan   

  1. Department of Chemistry, College of Science, Shanghai University, Shanghai 200444, P. R. China
  • Received:2014-12-25 Revised:2015-02-09 Published:2015-05-08
  • Contact: REN Qing-Hua
  • Supported by:

    The project was supported by the High Performance Computing Platform of Shanghai University, China and Shanghai Higher Education Connotation Construction"085"Project"Materials Genome Engineering"Funding, China (B.58-B111-12-101, B.58-B111-12-103).


Mechanisms for the [Fe(MgBr)2] catalyzed cross-coupling reaction between ortho-chlorostyrene and phenylmagnesium bromide to form biaryl were studied using density functional theory (DFT) calculations. We investigated two mechanisms. Cycle A included three basic steps: (I) oxidation of [Fe(MgBr)2] to obtain [Ar- Fe(MgBr)], (II) addition to yield [Ar-(phenyl)-Fe(MgBr)2], and (III) reductive elimination to return to [Fe(MgBr)2]. Cycle B did not form [Ar-Fe(MgBr)]. In the first step, phenylmagnesium bromide attacks the intermediate of the oxidative addition directly before [Cl-Mg-Br] dissociates to form [Ar-Fe(MgBr)]. The catalytic Cycle B is favored over the catalytic Cycle Awhen considering the solvent effect. The rate-limiting step in the overall catalytic cycle for both Cycle A and Cycle B is the reductive elimination of [Ar-(phenyl)-Fe(MgBr)2] to regenerate the catalyst [Fe(MgBr)2], where the Gibbs free energy in solvent tetrahydrofuran (THF), ΔGsol, is 82.98 kJ ·mol-1, as determined using the conductor polarized continuum model (CPCM) method.

Key words: Iron catalyst, Biaryl, Cross-coupling, Reaction mechanism, Density functional theory


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