A high-spin iron(IV)-oxo complex supported by a trigonal nonheme pyrrolide platform

We report the generation and characterization of a new high-spin iron(IV)-oxo complex supported by a trigonal nonheme pyrrolide platform. Oxygen-atom transfer to [(tpa ^Mes)Fe ^II] ^- (tpa ^Ar = tris(5-arylpyrrol-2-ylmethyl)amine) in acetonitrile solution affords the Fe(III)-alkoxide product [(tpa ^Mes2MesO)Fe ^III] ^- resulting from intramolecular C-H oxidation with no observable ferryl intermediates. In contrast, treatment of the phenyl derivative [(tpa ^Ph)Fe ^II] ^- with trimethylamine N-oxide in acetonitrile solution produces the iron(IV)-oxo complex [(tpa ^Ph)Fe ^IV(O)] ^- that has been characterized by a suite of techniques, including mass spectrometry as well as UV-vis, FTIR, Mössbauer, XAS, and parallel-mode EPR spectroscopies. Mass spectral, FTIR, and optical absorption studies provide signatures for the iron-oxo chromophore, and Mössbauer and XAS measurements establish the presence of an Fe(IV) center. Moreover, the Fe(IV)-oxo species gives parallel-mode EPR features indicative of a high-spin, S = 2 system. Preliminary reactivity studies show that the high-spin ferryl tpa ^Ph complex is capable of mediating intermolecular C-H oxidation as well as oxygen-atom transfer chemistry.