S. Castillo et al., THEORETICAL-STUDIES ON HYDROGEN ACTIVATION BY IRIDIUM DIMERS, International journal of quantum chemistry, 70(4-5), 1998, pp. 1029-1035
The basic and fundamental mechanisms governing the catalytic reaction
of small iridium clusters with H-2 are presented here with the purpose
to determine its behavior in hydrogenation reactions. The iridium dim
er's lowest states in interaction with H-2 potential energy surface we
re obtained using ab initio multiconfigurational self-consistent-field
calculations (MC-SCF), with relativististic pseudopotentials. The ele
ctronic correlation contribution was included by configurations intera
ction (CI) calculations, which considered a variational part plus a se
cond-order perturbative part. The Ir-2 + H-2 reactions were developed
in the C-2v symmetry. The Ir-2's five lowest electronic states were de
termined, (5)Pi g(,) (3)Pi(g), (1)Sigma(g)(+), ( 3)Sigma(u)(+), and (5
)Sigma(g), and studied when reacted with H-2. It was found that the ir
idium dimer, in these five states, might capture and break the H-H bon
d, spontaneously in certain cases and after surmounting activation bar
riers in other cases. (C) 1998 John Wiley & Sons, Inc.