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A general method for synthesis of supported metal complexes having a high degree of uniformity has been developed, whereby organometallic precursors incorporating acetylacetonate (acac) ligands react with zeolites incorporating OH groups near Al sites. The method is illustrated by the reactions of Rh(acac)(CO)2 and of cis-Ru(acac)2(C2H4)2 with zeolites slurried in n-pentane at room temperature. The zeolites include HY, H-Beta, H-SSZ-42, H-Mordenite, and HZSM-5. Infrared (IR) and extended X-ray absorption fine structure spectra of the zeolites incorporating rhodium complexes indicate the formation from Rh(acac)(CO)2 of the supported complex Rh(CO)2+ bonded near Al sites. Similar results indicate the formation of zeolite-supported Rh(C2H4)2 from Rh(acac)(C2H4)2. Comparable chemistry takes place when the precursor is Ru(acac)2(C2H4)2, and an acac ligand is retained by the supported complex, and mixtures of the supported complexes are formed. Spectra of the supported metal gem-dicarbonyls include sharp, well-resolved ?CO bands, demonstrating that the sites surrounding each metal complex are nearly equivalent. The frequencies of the ?CO bands show how the composition of the zeolite influences the bonding of the supported species, demonstrating subtle differences in the roles of the zeolite as ligands. When the zeolite has pore openings larger than the critical diameter of the precursor organometallic compound, the latter undergoes facile transport into the interior of the zeolite, so that a uniform distribution of the supported species results, but when the precursors barely fit through the zeolite apertures, the mass transport resistance is significant and the supported metal complexes are concentrated near the pore mouths.

A set of supported ruthenium complexes with systematically varied ratios of chemisorbed to physisorbed species was formed by contacting the precursor cis-Ru(acac)2(C2H4)2 with dealuminated zeolite Y. These have been characterized in detail as catalysts for ethene conversion. EXAFS spectra characterizing the samples confirmed the systematic variation of the loadings of the two supported species and demonstrated that removal of bidentate acac ligands from the precursor accompanied the chemisorption to form Ru(acac)(C2H4)22+ at Al sites of the zeolite attached through two Ru–O bonds. When the ruthenium loading exceeded 1.0 wt% (Ru/Al exceeding 1/6), the adsorbed species were simply physisorbed. Ethene ligands on the chemisorbed species reacted to form butenes when the temperature was raised to approximately 393 K; acac ligands remained bonded to Ru. In contrast, ethene ligands on the physisorbed complex simply desorbed under the same conditions. The chemisorption activated the ruthenium complex and facilitated dimerization of the ethene, which occurred catalytically. IR and EXAFS data characterizing the supported samples indicate that (1) Ru centers in the chemisorbed species are more electropositive than those in the physisorbed species and (2) Ru-ethene bonds in the chemisorbed species are less symmetric than those in the physisorbed species, implying the presence of a configuration preferred for the catalytic dimerization. The depth of understanding of the catalysis approaches that attainable for well-defined molecular catalysts in solution.