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Title:High Pressure Nuclear Magnetic Resonance Studies of Homogeneous Catalysts
Author(s):VanderVelde, David Gerald
Doctoral Committee Chair(s):Jonas, Jiri; Shapley, John R.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:The design and testing of a nuclear magnetic resonance probe for studying homogeneous catalysts from $-40\sp\circ$C to $100\sp\circ$C and pressures up to 4000 psi is described. Its significant features are a built-in stirring mechanism to mix the sample under study with reactive gases, and resolution and sensitivity comparable to that obtained in ambient-pressure probes without sample spinning. Well-known organometallic reactions are used to demonstrate the probe's capabilities.
A rhodium catalyst for converting syngas to oxygenated organic compounds is examined in two solvent systems, sulfolane/4-methylmorpholine and 1-methyl-2-pyrrolidinone, leading to identification of rhodium carbonyl anionic clusters present at ambient and extreme conditions. Clusters fragmented much more easily in the former solvent, leading to a smaller distribution of clusters and more pronounced changes in the clusters present with temperature and pressure changes. Hydrido carbonyl anions, expected to be catalytically important as the source of activated hydrogen, were completely absent except for a trace of H$\sb2$Rh$\sb $(CO)$\sb{24}\sp{3-}$.
Proton relaxation and site exchange processes in the metal clusters ($\mu$-H)$\sb3$M$\sb3$(CO)$\sb9(\mu\sb3$-CH)(M = Os,Ru) and ($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb (\mu$-CH$\sb2)/(\mu$-H)Os$\sb3$(CO)$\sb (\mu$-CH$\sb3$) are also studied. From relaxation rates, nuclear Overhauser enhancements, and spin saturation transfer, the exchange rates, activation parameters, and interproton distances are calculated for these clusters; the latter are compared with neutron diffraction measurements in the first two compounds. For the methyl compound, whose structure has not been solved by diffraction methods, the NMR data support a structure very similar to that of the methylene.
Issue Date:1987
Description:94 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
Other Identifier(s):(UMI)AAI8803226
Date Available in IDEALS:2014-12-15
Date Deposited:1987

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