Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity

Yuji Kikukawa; Kensuke Seto; Daiki Watanabe; Hiromasa Kitajima; Misaki Katayama; Shohei Yamashita; Yasuhiro Inada; Yoshihito Hayashi

doi:10.1002/anie.202007406

Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity

Angew Chem Int Ed Engl. 2020 Aug 17;59(34):14399-14403. doi: 10.1002/anie.202007406. Epub 2020 Jul 8.

Authors

Yuji Kikukawa^{1

2}, Kensuke Seto¹, Daiki Watanabe¹, Hiromasa Kitajima¹, Misaki Katayama³, Shohei Yamashita⁴, Yasuhiro Inada³, Yoshihito Hayashi¹

Affiliations

¹ Department of Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, 920-1192, Ishikawa, Japan.
² JST, PRESTO, 4-1-8 Honcho, Kawaguchi, 332-0012, Saitama, Japan.
³ Department of Applied Chemistry, Graduate School of Life Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, 525-8577, Shiga, Japan.
⁴ Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, 305-0801, Ibaraki, Japan.

PMID: 32511879
DOI: 10.1002/anie.202007406

Abstract

Dodecavanadate, [V₁₂ O₃₂ ]^4- (V12), possesses a 4.4 Å cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br₂ was inserted into V12, inducing the inversion of one of the VO₅ square pyramids to form [V₁₂ O₃₂ (Br₂ )]^4- (V12(Br2)). The inserted Br₂ molecule was polarized and showed a peak at 185 cm^-1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br₂ molecule. Compound V12(Br2) also reacted with propane, n-butane, and n-pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3-bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2-,3-dibromobutane and 2,3-dibromopenane. The unique inorganic cavity traps Br₂ leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br₂ shows selective functionalization of alkanes.

Keywords: alkane bromination; bromine polarization; molecular containers; polyoxometalates; vanadium.

Abstract

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