The development of selective catalysts for the multiproton-multielectron reduction of small molecule substrates is of significant interest. Metal-ligand cooperativity has been utilized to expand the reactivity of transition metals. To facilitate proton and electron transfer during dioxygen reduction, a ligand containing a redox-active hydroquinone moiety was prepared. A Pd(0)-hydroquinone complex was synthesized and found to rapidly react with dioxygen at room temperature to quantitatively yield the corresponding Pd(0)-quinone complex. Slower reactivity with dioxygen was observed with a (Pd-H)-hydroquinone complex at room temperature to cleanly yield the protonated Pd(0)-quinone complex. Structure-reactivity studies were conducted using a Ag(I)-hydroquinone complex and a Pd(0) complex with a redox-inactive para-methoxy-substituted central arene as probes for ligand-only and Pd-only reactivity respectively. The mechanism of dioxygen reaction and product selectivity was studied by variable temperature NMR, gas quantification by Toepler pump, and UV/Vis and solution IR spectroscopy.

Metal-ligand cooperativity in Pd-hydroquinone complexes for dioxygen reduction

248th National Meeting (2014)

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