We have synthesized novel La2/3-xTiO3-3x(OH)(3x) (0.07 < x < 0.13) compounds by ion exchange of the lithium ions from La2/3-xLi3xTiO3 in dilute HNO3 at 60 degrees C. The proton derivatives crystallize in tetragonal perovskite cells (a approximate to a(p), c approximate to 2a(p)) similar to those of the parent oxides. Interestingly, the protonated oxides (characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and H-1 nuclear magnetic resonance (NMR) yield new metastable A-site- and oxygen-deficient perovskites La2/3-xTiO3-3x/2 at about 800 degrees C.