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Issue 44, 2016
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Alkyl Grignard cross-coupling of aryl phosphates catalyzed by new, highly active ionic iron(II) complexes containing a phosphine ligand and an imidazolium cation

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Abstract

A novel family of ionic iron(II) complexes of the general formula [HL][Fe(PR′3)X3] (HL = 1,3-bis(2,6-diisopropylphenyl)imidazolium cation, HIPr, R′ = Ph, X = Cl, 2; HL = HIPr, R′ = Cy, X = Cl, 3; HL = HIPr, R′ = Ph, X = Br, 4; HL = HIPr, R′ = Cy, X = Br, 5; HL = 1,3-bis(2,4,6-trimethylphenyl)imidazolium cation, HIMes, R′ = Cy, X = Br, 6) was easily prepared via a stepwise approach in 88%–92% yields. In addition, an ionic iron(II) complex, [HIPr][Fe(C4H8O)Cl3] (1), has been isolated from the reaction of FeCl2(THF)1.5 with one equiv. of [HIPr]Cl in 90% yield and it can further react with one equiv. of PPh3 or PCy3, affording the corresponding target iron(II) complex 2 or 3, respectively. All these complexes were characterized by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), 1H NMR spectroscopy and X-ray crystallography. These air-insensitive complexes 2–6 showed high catalytic activities in the cross-coupling of aryl phosphates with primary and secondary alkyl Grignard reagents with a broad substrate scope, wherein [HIPr][Fe(PCy3)Br3] (5) was the most effective. Complex 5 also catalyzes the reductive cross-coupling of aryl phosphates with unactivated alkyl bromides in the presence of magnesium turnings and LiCl, as well as the corresponding one-pot acylation/cross-coupling sequence under mild conditions.

Graphical abstract: Alkyl Grignard cross-coupling of aryl phosphates catalyzed by new, highly active ionic iron(ii) complexes containing a phosphine ligand and an imidazolium cation

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Publication details

The article was received on 28 Jul 2016, accepted on 26 Sep 2016 and first published on 04 Oct 2016


Article type: Paper
DOI: 10.1039/C6DT02995G
Citation: Dalton Trans., 2016,45, 17739-17747
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    Alkyl Grignard cross-coupling of aryl phosphates catalyzed by new, highly active ionic iron(II) complexes containing a phosphine ligand and an imidazolium cation

    Z. Li, L. Liu, H. Sun, Q. Shen and Y. Zhang, Dalton Trans., 2016, 45, 17739
    DOI: 10.1039/C6DT02995G

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