Density functional study of multiple H2 adsorption and activation on a Pd6 cluster

Density functional calculations are used to determine structures and stabilities of Pd6 and hydride complexes Pd6(H)n (n=2,4). Calculations show that a triplet state of Pd6 with an elongated octahedral structure is the ground state and the Pd6 cluster can activate the second H2 molecule. Barriers of the rate-determining steps for the first H2 and the second H2 activation process are ca. 11 kcal/mol and ca. 7–9 kcal/mol, respectively. In the dihydrogen complexes, the H2-ligand behaves as donor in the molecular bonding between H2 and Pd6. Chemisorbed hydrogen atoms prefer to bridge the Pd–Pd edges in the most stable hydride complexes Pd6(H)n (n=2,4).