The metal centres of LA-TM (Lewis Acid -Transition Metal) complexes, which have a great influence on the activation of hydrogen, will be discussed with reference to a series of tris(phosphino) borane (TPB) complexes with certain investigated transitional metals (e.g., V, Cr, Mn, Fe, Co, and Ni). According to the figure , based on the DFT (Density functional theory) calculations, TPB complexes of V, Cr, Mn, Fe, and Co have the tendency to prefer the stepwise mechanism for the activation of hydrogen molecules, while TPB-Ni favours a synergetic mechanism for H2 activation.