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

Dodecavanadate, [V12O32](4-)(V12), possesses a 4.4 angstrom 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 [V12O32(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.