Reactivity of aluminium dimer with H2: the performance of high level ab initio and density functional methods for prediction of reaction paths

The Cs and C2v paths of the Al 2 ( 3 Π u , 1 Σ g + ) + H 2 reaction to form the singlet dibridged Al(μ-H)2Al product, detected repeatedly in solid matrices, has been investigated. The performance of a number of high level single-reference and CASSCF based ab initio and DFT methods are compared. The key finding is that the two singlet routes involve no energetic barrier for the HH bond breakage relative to the singlet reactants. The theoretical results are in accord with the recent experimental observation that Al2 dimer reacted spontaneously with H2 in solid matrix.