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

YooJin Kim, Xudong Feng, and Stephen J. Lippard*
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
Inorg. Chem., 2007, 46 (15), pp 6099–6107
DOI: 10.1021/ic700622a
Publication Date (Web): June 19, 2007
Copyright © 2007 American Chemical Society
*

 To whom correspondence should be addressed. E-mail:  lippard@ mit.edu.

Abstract

Abstract Image

The purple triiron(II,III,III) complex, [Fe3Cl2(TMRASQ)4(HTMRA)2]·C5H12 (1·C5H12), where H2TMRA 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 H2TMRA and characterized by X-ray crystallography, Mössbauer 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 H2AA analogue, 1 provides insight into the possible coordination geometry of the family of complexes containing H2AA and its analogues. In the presence of air and H2TMRA, 1 is able to catalyze the oxidation of cyclohexane to cyclohexanol with remarkable selectivity, but the nature of the true catalyst remains unknown.

View: Full Text HTML | Hi-Res PDF

Tools

History

  • Published In Issue July 23, 2007
  • Received April 1, 2007

Recommend & Share

Related Content

Other ACS content by these authors: