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 K₂Fe^II[Fe^II(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.