The D 0 values for AlH 2 and AlAr are computed using the coupled cluster approach in conjunction with large basis sets. Basis set superposition and spin-orbit effects are accounted for, as they are significant due to the small binding energy. The computed dissociation energy (D 0 ) for AlAr is 114 cm - 1 , which is 93% of the experimental value (122.4 cm - 1 ). Our best estimate for the Al-H 2 binding energy is 38 ± 26 cm - 1 .