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- Title
On the Lewis Acidity of the Oxoiron(IV) Unit in a Tetramethylcyclam Complex.
- Authors
Klein, Johannes E. M. N.; Draksharapu, Apparao; Shokri, Alireza; Cramer, Christopher J.; Que, Jr., Lawrence
- Abstract
Abstract: The correlation between oxidation state and Lewis acidity is well established for hexaquairon complexes in the +II and +III oxidation state, in which the higher oxidation state leads to a lower p<italic>K</italic>a for the bound H2O ligand. This article addresses the Lewis acidity of the oxoiron(IV) complex [FeIV(O)(TMC)(OH2)]2+ (<bold>1‐OH2</bold>; TMC=1,4,8,11‐tetramethylcyclam) by determining the p<italic>K</italic>a of the H2O ligand. We establish that <bold>1‐OH2</bold> has a p<italic>K</italic>a of 6.9±0.5, a value that falls in between those found for [FeIII(OH2)6]3+ and [FeII(OH2)6]2+. This intermediate value can be readily rationalized by the presence of the highly basic oxide ligand that mitigates the Lewis acidity of the iron(IV) center. Although the oxo ligand occupies only one position in <bold>1‐OH2</bold>, <italic>anti</italic> to all four methyl groups that protrude from the same face of the nonplanar TMC ligand, its conjugate base <bold>1‐OH</bold> exists as a mixture of <italic>syn</italic> and <italic>anti</italic> tautomers, which are related by proton transfer between the oxo and the hydroxo ligands.
- Subjects
OXIDATION states; LEWIS acidity; LIGANDS (Chemistry); METHYL groups; HYDROCARBONS
- Publication
Chemistry - A European Journal, 2018, Vol 24, Issue 20, p5373
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201704977