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

Dodecavanadate, [V 12 O 32 ] 4− (V12), possesses a 4.4 Å cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br 2 was inserted into V12, inducing the inversion of one of the VO 5 square pyramids to form [V 12 O 32 (Br 2 )] 4− (V12(Br2)). The inserted Br 2 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 Br 2 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 Br 2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br 2 shows selective functionalization of alkanes.