Non-heme iron nitrosyl complexes in different oxidation states are not only important intermediates in denitrification and NO reduction, but also serve as platforms for NO sensing and potentially HNO generation in biology.1 In order to better understand the potential roles that non-heme iron centers could play in this context, it is important to prepare corresponding, biomimetic model systems and study their redox-interconversions and their biologically-relevant reactivity. Much progress has been made in this regard with respect to heme-nitrosyls and corresponding models,2 whereas our knowledge about non-heme iron NO complexes in different oxidation states is sparse. We have used the TMG3tren ligand platform to prepare the {FeNO}7 complex (in the Enemark-Feltham notation) [Fe(TMG3tren)(NO)](OTf)2 (see Figure) and then investigated the redox interconversion of this complex.3 Excitingly, in this way we were able to prepare the complete series of high-spin {FeNO}6 – {FeNO}8 complexes and we characterized the spectroscopic properties and reactivities of these complexes in detail. Importantly, our results show that all redox-interconversions along this series of complexes are metal based, spanning a range from Fe(IV) to Fe(II) complexes with a bound triplet NO(-), or nitroxyl, ligand. In addition, the {FeNO}8 complex can be protonated, generating the first non-heme iron(II)-HNO complex. References: Speelman, A.; Lehnert, N. Heme versus Non-Heme Iron-Nitroxyl {FeN(H)O}8 Complexes: Electronic Structure and Biologically Relevant Reactivity. Acc. Chem. Res. 2014, 47, 1106-1116. Goodrich, L. E.; Paulat, F.; Praneeth, V. K. K.; Lehnert, N. Electronic Structure and Reactivity of Heme-Nitrosyls and Its Significance for Nitric Oxide Sensing, Transport, and Catalysis in Biological Systems. Inorg. Chem. 2010, 49, 6293–6316. Speelman, A. L.; Lehnert, N. Characterization of a High-Spin Non-Heme {FeNO}8 Complex: Implications for the Reactivity of Iron Nitroxyl Species in Biology. Angew. Chem. Int. Ed. 2013, 52, 12283-12287.

From non-heme {FeNO}6 to Fe(II)-HNO complexes: One ligand platform can do it all

251st National Meeting (2016)

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