Understanding the protonation of metal oxides and the dynamics of proton transfer on metal oxide surfaces is critical to the development of several key technologies including proton conducting membranes and catalysis.  We are interested in studying these fundamental processes using simpler homogeneous models.  Recently, we established that in nonaqueous media, the inorganic proton cryptates of metatungstate, a-[(H_x)W₁₂O₄₀]^(8-x)-, exist in two protonation states (x = 2, 3) with the protons located within the internal cryptand cavity.  They are isolated as the tetra-n-butylammonium (Q⁺) salts, Q₆[a-(H₂)W₁₂O₄₀] (1) and Q₅[a-(H₃)W₁₂O₄₀] (2).  Since an activation barrier is expected for an external proton to transfer across the close-packed oxide surface of 1 to form 2, it is surprising that the transformation is instantaneous by ¹H NMR (1 equiv of HBr in CH₃CN), whereas the reverse process is slow (t_1/2 ~ 17.4 h; 1 equiv of Q⁺OH^-).  We report preliminary mechanistic investigations of these processes.