Anhydrous $AlCl_3$ is covalent but $AlCl_3.6H_2O$ is ionic because
(1) $AlCl_3$ has a planar triangular structure
(2) The ionization energy of $Al$ is very low
(3) The hydration energy of $AlCl_3$ is very low
(4) The hydration energy of $AlCl_3$ compensates for the high ionization energy of aluminum
