DFT and CCSD(T) study of the A2H3− (A = Al, Ga) isomerization, [Ga2(μ-H)(μ-H2)]− and [Ga2(μ-H3)]− unprecedented hydrido-bimetallic structures

Total potential energy surfaces (PES) are scanned in order to study the isomerization of the A2H3− (A = Al, Ga) anions. Al2H3− PES is characterized by six minima and seven transition structures which are connectable with themselves. Indeed of these 12 same extrema, the Ga2H3− PES has three other minima and four TSs. These structures exhibit an activated H2 molecule in one or both Ga atoms coordination sphere where the Ga atom seems imply its metallic character via its occupied d-orbital. We have also localized two unusual structures: a minimum having M2(μ-H)(μ-H2)-like structure and a transition with M2(μ-H3)-like arrangement where the H3 entity is coordinated to both Ga atoms. The connectivity of all these extrema brings to the fore an eventual fluxional behaviour of these compounds.