<title>Surface carbonyl species on highly dealuminated NaY zeolite: an FTIR investigation</title>

Abstract

FT-IR spectroscopy has been used to study the rather rich surface chemistry of Rh, Ir and Ru supported on zeolites. Highly dealuminated zeolite Y (US-Ex) has proved to be an ideal matrix for the formation of well defined surface carbonyls with unusually sharp carbonyl stretching bands. As the result, dicarbonyls of Rh and Ir and a tricarbonyl of Ru could be clearly identified on the surface.

Homogeneity of Surface Sites in Supported Single-Site Metal Catalysts: Assessment with Band Widths of Metal Carbonyl Infrared Spectra

“…For comparison of the supported species with dissolved molecular species, we determined fwhm values for the CO bands of the pure precursor Ir­(CO) 2 (acac) dissolved in mixed hexanes; the values are 3.9 and 4.0 cm –1 for the symmetric and asymmetric stretches at 2074 and 2000 cm –1 , respectively (Table and Figure ); as best we can tell, these data match within error those already reported for Ir­(CO) 2 (acac) in hexane . The weak bands at 2056 and 1967 cm –1 have been assigned as natural-abundance 13 CO stretching bands …”

“…27 The weak bands at 2056 and 1967 cm −1 have been assigned as natural-abundance 13 CO stretching bands. 28 Most important for our work, the fwhm values of the dissolved iridium complex are only slightly less than those observed for the HY zeolite-supported sample made in the lowtemperature synthesis (Figure 2). The bands characterizing this zeolite-supported iridium gem-dicarbonyl are as narrow as any reported for such a supported species and, to our knowledge, are consistent with the inference that it is the most nearly uniform supported single-site catalyst known.…”