What happens when vanadium dioxide reacts with a base?

Vanadium dioxide (${\text{VO}}_2$) is an amphoteric oxide, meaning it possesses the chemical ability to react as either an acid or a base depending on its environment.1

When vanadium dioxide reacts with a base, it dissolves to yield the yellow-brown hypovanadate ion, represented by the chemical formula $[{\text{V}}_4{\text{O}}_9{]}^{2-}$. This behavior is characteristic of its amphoteric nature, which allows it to dissolve in basic solutions just as it dissolves in acidic solutions to form the blue vanadyl ion, $[\text{VO}{]}^{2+}$.1