Skip to main content
Article
Oxygen Atom Transfer Reactions of Chromium Porphyrins: An Electronic Rationale for Oxo Transfer versus μ-Oxo Product Formation
Journal of the American Chemical Society
  • L. Keith Woo, Iowa State University
  • James G. Goll, Iowa State University
  • Lisa Mary Berreau, Iowa State University
  • Rob Weaving, Iowa State University
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
9-1-1992
DOI
10.1021/ja00045a012
Abstract
Treatment of (meso-tetra-p-tolylporphyrinato)chromium(IV) oxide, {TTP)Cr=O, with (octaethylporphyrinato)chromium( III) chloride, (OEP)Cr-Cl, in benzene results in the reversible exchange of axial ligands to form (TTP)Cr-Cl and (OEP)Cr=O. The net result is a formal one-electron redox process. This occurs with a second-order rate constant of 0.14 :1:: 0.01 M-1 s-1 to form an equilibrium mixture with K = 2.7 :1:: 0.1 at 30 °C (ill/* = 15.4 :1:: 0.7 kcaljmol, M* = -12 :1:: 2 cal/ (mol·K), ill/0 = -2.0 :1:: 0.4 kcaljmol, and M 0 = -4.6 :1:: 1.2 cal/ (mol·K)). Use of pivalate in place of chloride on the Cr(III) complex causes no significant change in the rate of this one-electron redox process. The sterically protected Baldwin's C2-capped {porphyrinato)chromium(III) complex, (CAP)Cr-Cl, also undergoes oxygen atom transfer with (OEP)Cr=O at a similar rate. In addition, excess chloride inhibits the rate of oxygen transfer with chlorochromium(III) complexes. These results support an inner-sphere mechanism involving a ~-oxo intermediate which is formed after an initial ligand (chloride or pivalate) dissociation from the chromium(III) reductant.
Comments

Reprinted (adapted) with permission from Journal of the American Chemical Society 114 (1992): 7411, doi:10.1021/ja00045a012. Copyright 1992 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
L. Keith Woo, James G. Goll, Lisa Mary Berreau and Rob Weaving. "Oxygen Atom Transfer Reactions of Chromium Porphyrins: An Electronic Rationale for Oxo Transfer versus μ-Oxo Product Formation" Journal of the American Chemical Society Vol. 114 Iss. 19 (1992) p. 7411 - 7415
Available at: http://works.bepress.com/l-woo/93/