Site-Isolated Molecular Iridium Complex Catalyst Supported in the 1-Dimensional Channels of Zeolite HSSZ-53: Characterization by Spectroscopy and Aberration-Corrected Scanning Transmission Electron Microscopy

Zeolite HSSZ-53, which has 1-dimensional channels with 14-ring extra-large pores, was used as a support for a molecular iridium complex synthesized from Ir(C2H4)2(C5H7O2) and characterized with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies and atomic-resolution aberration-corrected scanning transmission electron microscopy (STEM). The spectra show that Ir(C2H4)2(C5H7O2) reacted readily with the bridging OH groups of the zeolite, leading to the removal of C5H7O2 ligands and the formation of mononuclear Ir(C2H4)2 complexes bonded to the zeolite by Ir–O bonds at the framework aluminum sites. STEM images confirm the spectra, showing site-isolated iridium centers within the zeolite channels, with no evidence of iridium clusters. The samples constitute a highly uniform, well-defined array of essentially molecular catalytic species in a highly uniform, confined environment, allowing precise investigations of the chemistry of the iridium complex in the absence of solvents. IR s...