Characterization of neutral metal hydride-hydroxide hydrogen-bonded clusters HMOH(H2O)2 (M = Al and Ga)†

Metal hydride-hydroxide hydrogen-bonded clusters HMOH(H2O)n are key intermediates in the reactions of metals with water. However, characterizing the structure of such neutral clusters poses a challenging experimental goal due to the difficulty of size selection. Here, neutral HMOH(H2O)2 (M = Al and Ga) clusters were prepared by using a laser-vaporization source and characterized by size-specific infrared-vacuum ultraviolet spectroscopy combined with quantum chemical calculations and ab initio molecular dynamics simulations. The HMOH(H2O)2 (M = Al and Ga) clusters were found to have intriguing hydrogen-bonded network structures. The results indicate that the formation of HMOH(H2O)2 (M = Al and Ga) is both thermodynamically exothermic and kinetically facile in the gas phase. The present system serves as a model for capturing key intermediates in the metal-water reactions and also opens new avenues for systematic studies of a large variety of reactions between neutral metal atoms/clusters and small molecules.