Powdered VOPO4 . 2H2O suspended in excess neat aniline gives intercalation compounds VOPO4 . (H2O)x . (PhNH3+)y (0.6<x<1.1; 0.5<y<1.0) with the reduction of the V(V) to V(IV) state. The compounds with y>0.7 lead to the polymerization of the cation by addition of the Cu(II) ion to afford polyaniline. Suspended VOPO4 . 2H2O powders react with PhNH3+Cl-dissolved in ethanol to give the compound intercalated with both the anilinium cation and polyaniline.