NMR TECHNIQUES FOR STUDIES OF HOMOGENEOUS CATALYSIS

Sapphire NMR tubes have proven to be particularly useful for studying catalytic reactions under conditions of moderate pressure (viz, 100-2000 psi). The tubes, which are commercially available, are grown as single crystals in the required shape and used without further machining. A nonmagnetic valve caps the tube and is used both for the introduction of reactant gases and for making the static seal. Inert gases may also be used to pressurize the sample for high-temperature studies in relatively low-boiling solvents. In addition to straightforward kinetic studies, we have frequently found that magnetization-transfer studies of slow exchange are uniquely well suited to unraveling discrete equilibria in catalytic cycles. Examples involving reactions of CO and C2H4 are described.