Chasing the Evasive Fe=O Stretch and the Spin State of the Iron(IV)-Oxo Complexes by Photodissociation Spectroscopy

0471901 - ÚFCH JH 2018 RIV US eng J - Journal Article
Andris, E. - Navrátil, R. - Jašík, J. - Terencio, T. - Srnec, Martin - Costas, M. - Roithová, J.
Chasing the Evasive Fe=O Stretch and the Spin State of the Iron(IV)-Oxo Complexes by Photodissociation Spectroscopy.
Journal of the American Chemical Society. Roč. 139, č. 7 (2017), s. 2757-2765. ISSN 0002-7863. E-ISSN 1520-5126
R&D Projects: GA ČR(CZ) GJ15-10279Y
Grant - others:GA MŠk(CZ) LM2010005
Institutional support: RVO:61388955
Keywords : Coordination reactions * Inorganic compounds * Ligands
OECD category: Physical chemistry
Impact factor: 14.357, year: 2017

We demonstrate the application of infrared photodissocation spectroscopy for determination of the Fe=O stretching frequencies of high-valent iron(IV)-oxo complexes [(L)Fe(O)(X)]2+/+ (L = TMC, N4Py, PyTACN, and X = CH3CN, CF3SO3, ClO4, CF3COO, NO3, N3). We show that the values determined by resonance Raman spectroscopy in acetonitrile solutions are on average 9 cm-1 red-shifted with respect to unbiased gas-phase values. Furthermore, we show the assignment of the spin state of the complexes based on the vibrational modes of a coordinated anion and compare reactivities of various iron(IV)-oxo complexes generated as dications or monocations (bearing an anionic ligand). The coordinated anions can drastically affect the reactivity of the complex and should be taken into account when comparing reactivities of complexes bearing different ligands. Comparison of reactivities of [(PyTACN)Fe(O)(X)]+ generated in different spin states and bearing different anionic ligands X revealed that the nature of anion influences the reactivity more than the spin state. The triflate and perchlorate ligands tend to stabilize the quintet state of [(PyTACN)Fe(O)(X)]+, whereas trifluoroacetate and nitrate stabilize the triplet state of the complex.
Permanent Link: http://hdl.handle.net/11104/0269276