Infrared spectra of [Mg·(H2O)1,2]+ and [Al·(H2O)1,2]+ are measured in the OH stretching region (3200-3800 cm-1). The spectra show the symmetric and asymmetric OH stretching bands of water molecules that are directly bound to the metal ions through metal-oxygen intermolecular bonds. In addition to these bands, the [Al·(H2O)2]+ ion has another band at 3714 cm-1. This band is assigned to the free OH stretching vibration of the [HO-Al-H]+ ion; the aluminum ion is inserted into the O-H bond of one water molecule in [Al·(H 2O)2]+.