Reaction of gallium dimer with H2: a theoretical study of the process mechanism

The reaction of Ga2 with H2 to form the most stable singlet Ga(μ-H)2Ga isomer 1 observed to occur spontaneously in solid noble gas matrices by Downs has been investigated theoretically with single- and multi-reference ab initio and DFT methods. Early on the reaction coordinate, a spin crossing is expected to move the process from the reactant ground-state triplet surface onto the singlet surface of the product. The singlet direct C2v path involves the most favourable TSPH-H activation transition state lying, at CCSD(T), 2.7 kcal/mol above Ga 2 ( 1 Σ g + ) + H 2 .