Chemical mechanism of dioxygen activation by trans-[FeCl2(cyclam)]+(cyclam = 1,4,8,11-tetraazacyclotetradecane) in the presence of reducing agents such as aliphatic aldehydes or linolenic acid

Abstract

The complex trans-[FeCl₂(cyclam)]⁺(cyclam = 1,4,8,11-tetraazacyclotetradecane) was found to activate dioxygen in the presence of reducing agents such as an aliphatic aldehyde or linolenic acid (octadeca-9,12,15-trienoic acid), leading to degradation of tetraphenylcyclopentadienone. The activity of the corresponding cis isomer is almost negligible. The origin of the high activity of the trans compound is discussed in terms of the results of extended-Hückel molecular-orbital calculations performed for the assumed intermediate. It is concluded that the formation of hydrogen bonding between dioxygen and the ligand is very important for activation of dioxygen in this system.