The oxygenation of cyclohexane under GifIV conditions – The catalytic behaviour of iron complexes

The catalytic oxygenation of cyclohexane to cyclohexanol (-ol) and cyclohexanone (-one) using a series of di- and trivalent iron-picolinate complexes under GifIV conditions (10:1 v/v pyridine–acetic acid, zinc powder at room temperature under aerobic atmosphere) proceeds with turnover numbers [defined as (moles of oxygenated products)/(moles of catalyst)] of 161–184 and -one:-ol ratios of 4.2–4.7. The corresponding values for the binuclear picolinate complex [Fe2(μ-OMe)2(pic)4] (237 turnovers, -one:-ol ratio 7.2) are significantly higher. Iron complexes bearing functionalised pyridyl ligands exhibit turnover numbers and ketone selectivities of similar magnitude to, and in some cases higher than, the picolinate complexes.