The role of substrate in unmasking oxyl character in oxomanganese complexes: the key to selectivity?

Sameera, W. M. C. and McGrady, J. E. (2008) The role of substrate in unmasking oxyl character in oxomanganese complexes: the key to selectivity? Dalton Transactions(44), pp. 6141-6149. (doi: 10.1039/b809868a)

Abstract

The reaction profile for sulfide oxidation by formally Mn(v)=O species depends critically on the electronic structure of the isolated oxidant. In cases where the ground state has dominant oxyl radical character, the oxidation occurs in sequential one-electron steps, the first of which is barrierless. In contrast, if the oxyl radical character is 'masked' in the ground state by electron transfer from either the metal or the porphyrin co-ligand, the interaction between oxidant and substrate is repulsive at large separations, only becoming attractive when the incoming nucleophile approaches close enough to drive an electron out of oxide p pi manifold, thereby 'unmasking' the oxyl radical. The shape of the repulsive wall at long range will depend on the properties of both oxidant and substrate, offering the potential for substrate discrimination that is one of the most remarkable properties of the oxygen evolving complex. The electronic properties of the oxidant depend critically on the identity of the axial co-ligand, but also on the chosen density functional. As a result, hybrid and non-hybrid functionals give very different qualitative descriptions of the oxidation reaction.

• Item Type: Articles
• Keywords: C-H HYDROXYLATION COMPLEX COMPLEXES COMPOUND-I DENSITY DINUCLEAR MANGANESE(IV) COMPLEX ELECTRON-TRANSFER ELECTRONIC-STRUCTURE GROUND-STATE HIGH-SPIN MANGANESE(III) HYBRID HYDROGEN-PEROXIDE MEDIATED ALKENE EPOXIDATION O BOND FORMATION OXIDATION OXIDE OXYGEN-EVOLVING COMPLEX PROFILE REBOUND MECHANISM Selectivity STATE STEP Structure
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McGrady, Prof John
• Authors: Sameera, W. M. C., and McGrady, J. E.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Dalton Transactions
• ISSN: 1477-9226