Selective conversion of CO into methanol at ordinary temperature. Part 4. Activation by iron(II), iron(III), and chromium(III) complexes

Abstract

The conversion of carbon monoxide into methanol has been performed at a platinum electrode modified with K2FeII[FeII(CN)6]. This reaction was activated by catalytic systems consisting of a primary alcohol and a series of iron(II), iron(III), or chromium(III) complexes. The current–time curves at a constant potential showed an oscillation, the period, induction time, and amplitude of which are a function of temperature, applied potential, and the nature and concentration of the metal complex or alcohol added. The pseudo-rate constant, the current efficiency, and the activation energy for the methanol formation have been determined. The current efficiency was almost 100% except in the presence of pentachlorochromate(III) and pentafluoroferrate(II), and the activation energy was 2.9–5.8 kcal mol–1 Infrared spectra of the metal complex isolated from the catalyst solution indicated that the reduction of CO takes place via methyl formate as an intermediate. These results are suggestive of a mechanism in which co-ordination of CO to the central metal in the form of methyl formate is a key step, and the diffusion of the co-ordinated species toward the modified electrode is rate determining.