A stable site-isolated mononuclear platinum catalyst with a well-defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from [Pt(NH3)4](NO3)2, oxidized at 633 K, and used to catalyze CO oxidation. IR and X-ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum-support bonding, and show that the platinum remained site isolated after oxidation and catalysis.

A stable site-isolated mononuclear platinum catalyst with a well-defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from [Pt(NH 3 ) 4 ]-(NO 3 ) 2 , oxidized at 633 K, and used to catalyze CO oxidation. IR and X-ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinumsupport bonding, and show that the platinum remained site isolated after oxidation and catalysis.

[Ir4(CO)12] and [Ir6(CO)16] were synthesized in the pores of zeolite NaY by reductive carbonylation of sorbed [Ir(CO)2(acac)], and [Rh6(CO)16] was similarly synthesized from [Rh(CO)2(acac)]. The supported metal carbonyl clusters were decarbonylated to give supported clusters modeled on the basis of extended X-ray absorption fine structure spectra as Ir4, Ir6, and Rh6, respectively. The supported metal carbonyl clusters and the supported metal clusters formed by their decarbonylation were investigated by 129Xe NMR spectroscopy at temperatures in the range of 100−305 K. As the temperature increased, the chemical shift decreased. The curves representing the chemical shift as a function of temperature for xenon sorbed on the zeolite that contained clusters modeled as Ir4, Ir6, and Rh6 were all essentially the same and hardly different from that observed for the bare zeolite NaY. This comparison leads to the conclusion that xenon is less strongly adsorbed on the decarbonylated metal clusters than on the zeolite framework. Larger chemical shifts were observed for the zeolites containing the metal carbonyl clusters, with the largest being observed for the zeolite containing [Ir4(CO)12]. These results are explained on the basis of the cluster sizes and NaY zeolite geometry. We suggest that the contact between xenon and [Ir4(CO)12] cluster is better than that between xenon and [Ir6(CO)16] or xenon and [Rh6(CO)16] clusters because these two larger clusters almost fill the zeolite supercages and exclude xenon, whereas [Ir4(CO)12] in the supercages is small enough to allow entry of the xenon.

Osmium carbonyls synthesized at low loadings in the supercages of zeolite NaX, including mononuclear osmium carbonyls and the following clusters, [HOs 3 (CO) 11 ] -, [H 3 Os 4 (CO) 12 ] -, and [Os 5 C(CO) 14 ] 2-, were identified by extended X-ray absorption fine structure and infrared spectroscopies. The samples were also characterized by 129 Xe NMR spectroscopy over the temperature range 100-310 K. The 129 Xe chemical shifts were greater for samples containing osmium carbonyls than for the bare zeolite over the entire temperature range. At the lowest temperatures, the chemical shifts representing xenon sorbed in the zeolites containing the osmium carbonyl clusters were essentially the same, but at temperatures close to room temperature, the chemical shift increased with decreasing size of the osmium carbonyl. The relatively large chemical shift observed for the smallest osmium carbonyl is consistent with the presence of Xe atoms in the cages with these mononuclear metal complexes, whereas Xe atoms barely fit into the cages with the larger [HOs 3 (CO) 11 ] -, [H 3 Os 4 (CO) 12 ] -, or [Os 5 C(CO) 14 ] 2-.