Electrocatalytic Alcohol Oxidation with Iron-Based Acceptorless Alcohol Dehydrogenation Catalyst

Electrochemical and chemical studies reveal that the amido complex (PNHP)Fe(CO)(H)(X) (FeN 1, x = 0, X = 0; Fe(H)(NH) 2, x = 1, X = H; PNHP = bis[2-(diisopropylphosphino)ethyl]amine) is active for the electrocatalytic oxidation of isopropanol. At room temperature, the amido FeN 1 dehydrogenates isopropanol to form acetone. The resulting amino hydride complex Fe(H)(NH) 2 is subsequently oxidized by one electron at a low potential (-0.74 V versus ferrocene/ferrocenium, Fc^0/+) in tetrahydrofuran. In the presence of strong base (phosphazene base P₂-Et, Et-N = P₂(dma)₅, P2), this oxidation process becomes a two-electron, two-proton process that regenerates FeN 1. FeN 1 is active for the electrooxidation of isopropanol in the presence of strong base (i.e., P2) with an onset potential near -1 V versus Fc^0/+. By cyclic voltammetry, fast turnover frequencies of 1.7 s^-1 for isopropanol oxidation are achieved with FeN 1. Controlled potential electrolysis studies confirm that the product of isopropanol electrooxidation is acetone, generated with high Faradaic efficiency (∼100%).