Halogen‐Bonding‐Assisted Iodosylbenzene Activation by a Homogenous Iron Catalyst. Issue 11 (24th November 2015)

• Record Type: Journal Article
• Authors: de Sousa, David P.; Wegeberg, Christina; Vad, Mads Sørensen; Mørup, Steen; Frandsen, Cathrine; Donald, William A.; McKenzie, Christine J.
• Is Part Of: Chemistry. Volume 22:Issue 11(2016)
• Page Start: 3810
• Page End: 3820
• Publication Date: 2015-11-24
• Subjects: epoxidation -- gas-phase chemistry -- halogen-bonding -- iodosylbenzene -- iron -- sulfoxidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201503112
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The iron(III) complex of hexadentate N, N, N ′‐tris(2‐pyridylmethyl)ethylendiamine‐ N ′‐acetate (tpena − ) is a more effective homogenous catalyst for selective sulfoxidation and epoxidation with insoluble iodosylbenzene, [PhIO] n, compared with soluble methyl‐morpholine‐ N ‐oxide (NMO). We propose that two molecules of [Fe(tpena)] 2+ cooperate to solubilize PhIO, extracting two equivalents to form the halogen‐bonded dimeric {[Fe(tpena)OIPh]2 } 4+ . The closest intradimeric I⋅⋅⋅O distance, 2.56 Å, is nearly 1 Å less than the sum of the van de Waals radii of these atoms. A correlation of the rates of the reaction of {[Fe(tpena)OIPh]2 } 4+ with para ‐substituted thioanisoles indicate that this species is a direct metal‐based oxidant rather than a derived ferryl or perferryl complex. A study of gas‐phase reactions indicate that an ion at m/z =231.06100 originates from solution‐state {[Fe(tpena)OIPh]2 } 4+ and is ascribed to [Fe III (tpenaO)] 2+, derived from an intramolecular O atom insertion into an Fe–tpena donor bond. Proposed ion pairs, {[Fe(tpena)OIPh]Cl} + and {[Fe(tpena)OIPh]ClO4 } +, are more stable than native [Fe(tpena)OIPh] 2+ ions, suggesting that halogen‐bonding, as for the solution and solid states, operates also in the gas phase. Abstract : Activation through halogen‐bonding : Stabilization of an iron(III)–OIPh complex in the gas, solution, and solid phases is ascribed to strong intermolecular halogen‐bonding. Two molecules of an iron(III) complex with a hexadentate ligand are proposed to work in unison to break the polymeric structure of [PhIO] n, concommitantly solubilizing and activating it to give a system that efficiently catalyzes the selective oxidation of electron‐rich substrates.