The H-2 release mechanism from phosphine borane and phosphine alane was investigated using quantum chemical methods (MP2/aug-cc-pVTZ geometry optimization and coupled-cluster energies were obtained through complete basis set extrapolation, CCSD(T)/CBS). The effect of catalysts borane, alane and galane on the processes was also explored. As the energy barriers for the release of H-2 from BH3PH3 and AlH3PH3 are much higher than the B-P and Al-P bond energies, the presence of inherent catalysts can reduce substantially such energy barriers (using BH3 for BH3PH3, while AlH3 and GaH3 for AlH3PH3), and these systems could be useful as probable hydrogen source. (C) 2013 Elsevier B. V. All rights reserved.