Synthesis and characterization of HY zeolite-supported rhodium carbonyl hydride complexes

Abstract

Abstract FTIR and EXAFS measurements, as well as results of isotope labeling experiments were used to characterize the species formed after grafting a Rh(CO) 2 (acac) precursor on a highly dealuminated HY zeolite and during subsequent ligand exchange reactions. The Rh(CO) 2 species initially formed rapidly react with C 2 H 4 to form Rh(CO)(C 2 H 4 ) complexes. Exposure of the latter to H 2 selectively yields Rh(CO)(H) x complexes, characterized by a set of well-defined ν CO and ν RhH bands in their FTIR spectra. The hydride ligands in these complexes can be displaced by CO and N 2 to form Rh(CO) 2 and Rh(CO)(N 2 ) complexes, respectively. In contrast, C 2 H 4 reacts with the hydrides, yielding C 2 H 6 and an unstable Rh(CO) intermediate. The latter rapidly reacts with additional gas-phase C 2 H 4 to reform the original Rh(CO)(C 2 H 4 ) complex. The Rh(CO)(H) x species were stable at room temperature under H 2 or He for an extended period of time, but the hydride ligands can be removed at elevated temperatures.