Sulfinato Iron(III) Complex for Electrocatalytic Proton Reduction

We
report the first example of a sulfinato Fe­(III) complex acting as
a highly active electrocatalyst for proton reduction. The sulfinate
binds to the metal through oxygen, resulting in a seven-membered chelate
ring that is likely hemilabile during catalysis. Proton reduction
occurs at −1.57 V versus Fc/Fc+ in CH3CN with an ic/ip = 13 in CH3CN (kobs = 3300 s–1) and an overpotential
of 800 mV. The catalysis is first order with respect to [catalyst]
and second order with respect to [trifluoracetic acid]. An 11% increase
in catalytic activity is observed in the presence of water, suggesting
that sulfinate moieties are viable functional groups for aqueous proton
reduction catalysts.