Octahedral iron()tosylimido complexes exhibiting single electron-oxidation reactivity

High valent iron species are very reactive molecules involved in oxidation reactions of relevance to biology and chemical synthesis. Herein we describe iron( iv )tosylimido complexes [Fe IV (NTs)(MePy 2 tacn)](OTf) 2 ( 1 (IV) &z.dbd;NTs ) and [Fe IV (NTs)(Me 2 (CHPy 2 )tacn)](OTf) 2 ( 2 (IV) &z.dbd;NTs ), (MePy 2 tacn = N -methyl- N , N -bis(2-picolyl)-1,4,7-triazacyclononane, and Me 2 (CHPy 2 )tacn = 1-(di(2-pyridyl)methyl)-4,7-dimethyl-1,4,7-triazacyclononane, Ts = Tosyl). 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs are rare examples of octahedral iron( iv )imido complexes and are isoelectronic analogues of the recently described iron( iv )oxo complexes [Fe IV (O)(L)] 2+ (L = MePy 2 tacn and Me 2 (CHPy 2 )tacn, respectively). 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs are metastable and have been spectroscopically characterized by HR-MS, UV-vis, 1 H-NMR, resonance Raman, Mssbauer, and X-ray absorption (XAS) spectroscopy as well as by DFT computational methods. Ferric complexes [Fe III (HNTs)(L)] 2+ , 1 (III) NHTs (L = MePy 2 tacn) and 2 (III) NHTs (L = Me 2 (CHPy 2 )tacn) have been isolated after the decay of 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs in solution, spectroscopically characterized, and the molecular structure of [Fe III (HNTs)(MePy 2 tacn)](SbF 6 ) 2 determined by single crystal X-ray diffraction. Reaction of 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs with different p -substituted thioanisoles results in the transfer of the tosylimido moiety to the sulphur atom producing sulfilimine products. In these reactions, 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs behave as single electron oxidants and Hammett analyses of reaction rates evidence that tosylimido transfer is more sensitive than oxo transfer to charge effects. In addition, reaction of 1 (IV) &z.dbd;NTs and 2 (IV) &z.dbd;NTs with hydrocarbons containing weak CH bonds results in the formation of 1 (III) NHTs and 2 (III) NHTs respectively, along with the oxidized substrate. Kinetic analyses indicate that reactions proceed via a mechanistically unusual HAT reaction, where an association complex precedes hydrogen abstraction. Octahedral iron( iv ) tosylimido complexes based in the tacn ligand scaffold exhibit single electron oxidation reactivity.