A Bowl-Type Dodecavanadate as a Halide Receptor

[Image: see text] The dodecavanadate framework, [V(12)O(32)](4–), exhibits a unique bowl-type structure with an open molecular oxide cage having a cavity diameter of 4.4 Å, and different synthetic paths were required to construct the bowl-type structure with a different guest. A new dodecavanadate, {(n-C(4)H(9))(4)N}(4)[V(12)O(32)(CH(3)NO(2))] (1), is synthesized with a nitromethane guest, which is stacked above the entrance of the hemisphere rather than fully occupying the cavity, and it enables a guest-capturing reaction, while retaining the anionic cage structure. Compound 1 is a good precursor for halide-centered dodecavanadates, {(C(2)H(5))(4)N}(5)[V(12)O(32)(X)] (X = Cl(–) (2), Br(–) (3), and I(–) (4)). The position of the halide inside the cavity correlates with the ionic radius of the guest; the small chloride ion sat at the far bottom, and the large iodide floated at the entrance. The inclusion reaction rates were estimated through (51)V NMR time-course measurements in nitromethane. The reaction rates increase in the order I(–) < Br(–) < Cl(–).