The dissolution of Al(OH)₃ by a solution of NaOH results in the formation of:

AI(OH)₃ dissolves in NaOH solution to give ${\mathrm{Al}\left(\mathrm{OH}\right)}_4^{-}$ ion which is supposed to have the octahedral complex species ${\left[\mathrm{Al}(\mathrm{OH}{)}_4{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\right]}^{-}$ in aqueous solution
$\mathrm{Al}(\mathrm{OH}{)}_3+\mathrm{NaOH}(\mathrm{aq})⟶{\left[\mathrm{Al}(\mathrm{OH}{)}_4{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\right]}^{-}(\mathrm{aq})+{\mathrm{Na}}^{+}(\mathrm{aq})$