Theoretical study of interaction of small clusters of IrPt with H2

Abstract

The study of the interaction of small clusters of IrPt with H2 is reported here through ab initio multiconfiguration self-consistent field (MC-SCF) calculations, plus extensive multireference configuration interaction (MR-CI), in its variational and perturbative modes. These calculations provide a cluster model for the activation of hydrogen by IrPt bimetallic catalysts. First, we studied the IrPt dimer interaction with H2. The five lowest states of the IrPt dimer are: 2Σ+, 2Δxy, 4Πyz, 4Σ+, and 4Δxy. For the IrPt dimer interaction with H2, we found that the IrPt dimer for both metal sides is able to capture the H2 molecule without any activation barriers, relaxing the H–H bond. The IrPt2 trimer interaction with H2 was also studied. The ground and the lowest states of the IrPt2 trimer are a 4A1 electronic state and a 4B2 electronic state, respectively. We found that for both metal sides, the IrPt2 cluster in its ground 4A1 and the low-lying 4B2 electronic states can spontaneously capture and break the hydrogen molecule. Large H–H relaxation is obtained and no activation barriers were found. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 657–663, 2000