The adsorption of N-2 on structurally well-defined dealuminated HY zeolite-supported iridium diethylene complexes was investigated. Iridium dinitrogen complexes formed when the sample was exposed to N-2 in H-2 at 298 K, as shown by infrared spectra recorded with isotopically labeled N-2. Four supported species formed in various flowing gases: Ir(N-2), Ir(N-2)(N-2), Ir(C2H5)(N-2), and Ir(H)(N-2). Their interconversions are summarized in a reaction network, showing, for example, that, in the presence of N-2, Ir(N-2) was the pre-dominant dinitrogen species at temperatures of 273-373 K. Ir(CO)(N-2) formed transiently in flowing CO, and in the presence of H-2, rather stable iridium hydride complexes formed. Four structural models of each iridium complex bonded at the acidic sites of the zeolite were employed in a computational investigation, showing that the calculated vibrational frequencies agree well with experiment when full calculations are done at the level of density functional theory, independent of the size of the model of the zeolite.
展开▼
