The dehydrogenation reaction for the Li-H...H-F system was examined using the density functional theory calculations. The main interest of this work is to demonstrate that the microsolvation effect can drive the initial Li-H...H-F complex transforming into the Li+...H-H...F-system with the formation of an H-H covalent bond. The H...H bonding pattern can be adjusted stepwise by increasing the number of surrounding water molecules. Some rationalization was provided to interpret the fact that the solvation on the fluorine side is more effective than on the lithium side. (c) 2006 Elsevier B.V. All rights reserved.