Oxygen Atom Transfer Reactions of Chromium Porphyrins: An Electronic Rationale for Oxo Transfer versus μ-Oxo Product Formation
Date
Authors
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Research Projects
Organizational Units
The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).
History
The Department of Chemistry was founded in 1880.
Dates of Existence
1880-present
Related Units
- College of Liberal Arts and Sciences (parent college)
Journal Issue
Is Version Of
Versions
Series
Department
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.