화학공학소재연구정보센터
Inorganic Chemistry, Vol.46, No.15, 6099-6107, 2007
Synthesis, structure, and properties of a mixed-valent triiron complex of tetramethyl reductic acid, an ascorbic acid analogue, and its relationship to a functional non-heme iron oxidation catalyst system
The purple triiron(II,III,III) complex, [Fe3Cl2(TMRASQ)(4)(HTMRA)(2)]center dot C5H12 (1 center dot C5H12), where H(2)TMRA is a tetramethyl reductic acid, 4,4,5,5-tetramethyl-2,3-dihydroxy-2-cyclopenten-1-one, and HTMRASQ is the semiquinone form of this ligand, was prepared from (Et4N)(2)[Fe2OCl6] and H(2)TMRA and characterized by X-ray crystallography, Mossbauer spectroscopy, and redox titrations. The physical properties of the complex in solution are consistent with its mixed-valent character, as delineated by a solid-state structure analysis. Assignments of the iron and ligand oxidation states in the crystal were made on the basis of a valence bond sum analysis and the internal ligand geometry. As the first well-characterized iron complex of an ascorbic acid H(2)AA analogue, 1 provides insight into the possible coordination geometry of the family of complexes containing H(2)AA and its analogues. In the presence of air and H(2)TMRA, 1 is able to catalyze the oxidation of cyclohexane to cyclohexanol with remarkable selectivity, but the nature of the true catalyst remains unknown.