Single‐Site Zeolite‐Anchored Organoiridium Carbonyl Complexes: Characterization of Structure and Reactivity by Spectroscopy and Computational Chemistry

Abstract

A family of HY zeolite-supported cationic organoiridium carbonyl complexes was formed by reaction of Ir(CO)2(acac) (acac = acetylacetonate) to form supported Ir(CO)2 complexes, which were treated at 298 K and 1 atm with flowing gas-phase reactants, including C2H4, H2, 12 CO, 13 CO, and D2O. Mass spectrometry was used to identify effluent gases, and infrared and X-ray absorption spectroscopies were used to characterize the supported species, with the results bolstered by DFT calculations. Because the support is crystalline and presents a nearly uniform array of bonding sites for the iridium species, these were characterized by a high degree of uniformity, which allowed a precise determination of the species involved in the replacement, for example, of one CO ligand of each Ir(CO)2 complex with ethylene. The supported species include the following: Ir(CO)2, Ir(CO)(C2H4)2, Ir(CO)(C2H4), Ir(CO)(C2H5), and (tentatively) Ir(CO)(H). The data determine a reaction network involving all of these species.

Isostructural Zeolite-Supported Rhodium and Iridium Complexes: Tuning Catalytic Activity and Selectivity by Ligand Modification

“…At 298 K and at 373 K, the iridium carbonyl complexes catalyzed ethylene hydrogenation without measurable oligomerization ( Table 2). The spectra recorded during catalysis at 373 K ( Figure 6) include both the band assigned to Ir(CO)(C 2 H 4 ) and a band at 2075 cm -1 assigned 33 to Ir(CO)(C 2 H 5 ) complexes.…”

Transmission and fluorescence X-ray absorption spectroscopy cell/flow reactor for powder samples under vacuum or in reactive atmospheres

“…4,5 Because many catalysts at various stages of preparation and use are reactive with O 2 , moisture, and/or CO 2 , they require handling in inert-atmosphere glove boxes and sealed sample transfer devices and XAS cells. 6 Metal loadings in the range of 0.1-1.0 wt. % are common in industrial catalysts, 7 and promoter loadings are commonly an order of magnitude lower.…”

High‐Energy‐Resolution X‐ray Absorption Spectroscopy for Identification of Reactive Surface Species on Supported Single‐Site Iridium Catalysts

“…[43] All calculations were done with the hybrid B3LYP exchange-correlation functional, [44][45][46] at the Douglas-Kroll-Hess second order scalar relativistic level [46][47][48] using geometries de-termined in our prior work. [29,30,49] Polarized double-z-DK basis sets were used. [50,51] FEFF and DOS modeling:H ERFD XANES spectra were simulated by use of the FEFF 9.7 code.…”

“…When Ir(CO) 2 on the HY zeolite [29] in the sample containing 1.0 wt. %I rw as exposed to flowinge thylene at 1bar and room temperature, a) n CH bands appeared at 3093, 3075, and 3022 cm À1 ( Figure 4A); and b) the n CO bands in the IR spectrum, at 2109 and 2038cm À1 ,d isappeared ( Figure 4B)a nd were replaced by bands at 2054 and 2087 cm À1 .T hese stretching frequencies have been assigned [6] to the CH and CO stretching frequencieso fs upported Ir(C 2 H 4 )(CO) and Ir(C 2 H 4 ) 2 (CO);t hese structures have been confirmed by EXAFS data.…”