ja7b00429_si_002.cif (508.72 kB)
Generation, Spectroscopic, and Chemical Characterization of an Octahedral Iron(V)-Nitrido Species with a Neutral Ligand Platform
dataset
posted on 2017-06-09, 00:00 authored by Gerard Sabenya, Laura Lázaro, Ilaria Gamba, Vlad Martin-Diaconescu, Erik Andris, Thomas Weyhermüller, Frank Neese, Jana Roithova, Eckhard Bill, Julio Lloret-Fillol, Miquel CostasIron
complex [FeIII(N3)(MePy2tacn)](PF6)2 (1), containing a neutral triazacyclononane-based
pentadentate ligand, and a terminally bound azide ligand has been
prepared and spectroscopically and structurally characterized. Structural
details, magnetic susceptibility data, and Mössbauer spectra
demonstrate that 1 has a low-spin (S = 1/2) ferric center. X-ray diffraction analysis of 1 reveals remarkably short Fe–N (1.859 Å) and long FeN–N2 (1.246 Å) distances, while the FT-IR spectra show an
unusually low N–N stretching frequency (2019 cm–1), suggesting that the FeN–N2 bond is particularly
weak. Photolysis of 1 at 470 or 530 nm caused N2 elimination and generation of a nitrido species that on the basis
of Mössbauer, magnetic susceptibility, EPR, and X-ray absorption
in conjunction with density functional theory computational analyses
is formulated as [FeV(N)(MePy2tacn)]2+ (2). Results indicate that 2 is a low-spin
(S = 1/2) iron(V) species, which exhibits a short
Fe–N distance (1.64 Å), as deduced from extended X-ray
absorption fine structure analysis. Compound 2 is only
stable at cryogenic (liquid N2) temperatures, and frozen
solutions as well as solid samples decompose rapidly upon warming,
producing N2. However, the high-valent compound could be
generated in the gas phase, and its reactivity against olefins, sulfides,
and substrates with weak C–H bonds studied. Compound 2 proved to be a powerful two-electron oxidant that can add
the nitrido ligand to olefin and sulfide sites as well as oxidize
cyclohexadiene substrates to benzene in a formal H2-transfer
process. In summary, compound 2 constitutes the first
case of an octahedral FeV(N) species prepared within a
neutral ligand framework and adds to the few examples of FeV species that could be spectroscopically and chemically characterized.