The performance of a supported metal catalyst is influenced by the structure of the metal species, the ligands bonded to the metal, and the support. Understanding of the role of ligands and supports can be maximized when the catalyst consists of the simplest metal species (uniform mononuclear metal complexes) bonded to uniform (i.e., crystalline) supports. Our goals were to gain understanding of the catalytic properties of supported iridium complexes formed by the adsorption of Ir(C2H4)2(C5H7O2). The zeolite was SSZ-53, with one-dimensional 14-ring channels. IR and EXAFS spectra characterizing the initially prepared sample indicate the formation of site-isolated Ir(C2H4)2 complexes bonded at Al centers of the zeolite, a result confirmed by aberration-corrected scanning transmission electron microscopy (STEM). This is a first example of well-defined metal complex anchored in one-dimensional zeolite channels. IR spectroscopy was used to track the reactions of Ir(C2H4)2 as it reacted with small ligands introduced from the gas phase:  CO, C2H4, and H2. The reactivity and catalytic activity of the Ir(C2H4)2 were compared with those of isostructural iridium complexes supported on MgO and zeolite HY. The catalyst was found to be active for ethylene hydrogenation and H�D exchange. The results allow an elucidation of the roles of the supports as ligands that, in combination with other ligands introduced from the gas phase, control the reactivity of the metal species and thereby the catalytic behavior in reactions that require activation of dihydrogen.

Molecular iridium catalysts in 1D channels of zeolite SSZ-53:  Probing support and ligand effects in catalysis of ethylene hydrogenation and H–D exchange in the conversion of H<sub>2</sub> + D<sub>2</sub>

243rd National Meeting (2012)

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Molecular iridium catalysts in 1D channels of zeolite SSZ-53: Probing support and ligand effects in catalysis of ethylene hydrogenation and H–D exchange in the conversion of H2 + D2

Molecular iridium catalysts in 1D channels of zeolite SSZ-53: Probing support and ligand effects in catalysis of ethylene hydrogenation and H–D exchange in the conversion of H₂ + D₂