(581d) Controlling Reactivity and Selectivity Using Self-Assembled Monolayers On Pd Catalysts

Performing selective conversions of reagents with multiple functional groups is a challenging objective since each group can potentially adsorb and react on a catalytic surface.  Our group has explored several techniques to promote selective reaction of a particular functional group including the modification of supported metal catalysts with organic ligands.  Alkanethiols can be deposited on supported metal catalysts to form organized self-assembled monolayers (SAMs) that can alter the selectivity of several catalytic reactions.  This attachment strategy was found to enhance the selectivity to the desired product during epoxybutene hydrogenation from 15% on uncoated catalysts to as high as 95% on SAM coated catalysts at equivalent reaction conditions. Selectivity of other reactions including 4-nitrostyrene hydrogenation is also strongly affected.  In this contribution, experiments aimed at identifying the mechanisms behind observed selectivity and activity trends will be described.  The effect of self-assembled monolayers on the hydrogenation of multifunctional compounds both in the liquid and gas phases will be discussed as well as methods for enhancing reaction rates by modifying thiol surface density.