ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 28, Number 6
JKCSEZ 28(6)
December 20, 1984 

Reaction of the Fe(Ⅱ) complex of a fully saturated tetradentate macrocyclic ligand [Fe([14]aneN4)(CH3CN)2]2+, where [14]aneN4 represents 1,4,8,11-tetraazacyclotetradecane, with O2 has been investigated in acetonitrile solutions. [Fe([14]aneN4)(CH3CN)2]2+ reacts with oxygen to yield low spin Fe(Ⅲ) species, [Fe([14]aneN4)(CH3CN)2]3+, which undergoes metal ion assisted oxidative dehydrogenation of the macrocyclic ligand to produce low spin Fe(Ⅱ) complex, [Fe([14]tetraeneN4)(CH3CN)2]2+. The macrocyclic ligand in [Fe([14]tetraeneN4)(CH3CN)2]2+ is highly unsaturated and its double bonds are conjugated. [Fe([14]dieneN4)(CH3CN)2]2+ and [Fe([14]dieneN4)(CH3CN)2]3+ are isolated as the intermediates of the reaction. The Fe(Ⅱ) complexes involved in this oxidative dehydrogenation reaction react with carbon monoxide to give respective carbon monoxide derivatives, [FeL(CH3CN)(CO)]2+ (where L = macrocyclic ligand). The values of νCO of [FeL(CH3CN)(CO)]2+, and the electrochemical oxidation potentials of Fe(Ⅱ) → Fe(Ⅲ) and the qualitative stability toward air-oxidation for [FeL(CH3CN)2]2+ increase as the degree of unsaturation of the macrocyclic ligands increase.