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Nuclear magnetic resonance investigations of zeolite-yttrium supported rhodium-carbon monoxide species
Abstract
The adsorbed states of CO on dispersed Rh on Y zeolites were studied using solid state $\sp{13}$C NMR. The structure of the Rh(CO)$\sb2$ form of adsorbed has been revealed using a Carr-Purcell-Meiboom-Gill multiple pulse sequence. Lineshape analysis has shown that the dicarbonyl pair undergoes a 180$\sp\circ$ flipping motion about the C$\sb2$ axis. Isolated dicarbonyls exhibit dipolar oscillations when irradiated in a Carr-Purcell-Meiboom-Gill experiment. The relative contributions to the total signal from oscillating and non-oscillating signal were used to determine the number of isolated adsorbed dicarbonyls. The oscillation pattern is that expected from isolated pairs of spin 1/2 nuclei, the Fourier transform of which is a Pake doublet. The frequency of the oscillation corresponds to an internuclear carbon-carbon distance of 2.58A. This agrees with the value of 2.63A found for inorganic rhodium dicarbonyls. Lineshapes have been calculated for adsorbed Rh(CO)$\sb2$ species undergoing 180$\sp\circ$ flipping motions. The resulting lineshapes are compared to published NMR spectra for dicarbonyls of Rh formed in Y-zeolites. The calculations predict the observed temperature dependence of the lineshapes and indicate an activation energy of 12kJ mol$\sp{-1}$ for the 180$\sp\circ$ flips.
Subject Area
Chemistry
Recommended Citation
Molitor, Paul Frederick, "Nuclear magnetic resonance investigations of zeolite-yttrium supported rhodium-carbon monoxide species" (1992). ETD collection for University of Nebraska-Lincoln. AAI9314419.
https://digitalcommons.unl.edu/dissertations/AAI9314419