Ab initio study on digallane(4), Ga₂H₄

The potential energy surface of digallane(4), Ga₂H₄, has been studied by ab initio molecular orbital theory at the MP2 level by using a Huzinaga valence triply ζ basis set supplemented with d-polarization functions. Six of the eight HF/3-21G* optimized structures were characterized as minima. Their bonding properties were studied by a topological electron density analysis. Of the ionic, covalent, and μ-hydrido bridged species the tri- and bidentate Ga⁺[GaH₄]^- forms are the most stable isomers. However, the energy differences with the other isomers are less than 15 kcal/mol. The covalent D_2d isomer 5 is 3.5 kcal/mol less stable than 1. The head and tail complexes of :GaH with GaH₃ (3 and 7), which are of similar energy, are ca. 13 kcal/mol higher in energy than 1. The potential energy surface of Ga₂H₄ is similar to that of Al₂H₄ but differences are noted.