Stable Ferrous Mononitroxyl {FeNO}8 Complex with a Hindered Hydrotris(pyrazolyl)borate Coligand: Structure, Spectroscopic Characterization, and Reactivity Toward NO and O2

Kiyoshi Fujisawa; Shoko Soma; Haruka Kurihara; Ayuri Ohta; Hai T Dong; Yurika Minakawa; Jiyong Zhao; E Ercan Alp; Michael Y Hu; Nicolai Lehnert

doi:10.1021/acs.inorgchem.9b00107

Stable Ferrous Mononitroxyl {FeNO}⁸ Complex with a Hindered Hydrotris(pyrazolyl)borate Coligand: Structure, Spectroscopic Characterization, and Reactivity Toward NO and O₂

Inorg Chem. 2019 Apr 1;58(7):4059-4062. doi: 10.1021/acs.inorgchem.9b00107. Epub 2019 Mar 13.

Authors

Affiliations

¹ Department of Chemistry , Ibaraki University , Mito 310-8512 , Japan.
² Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109 , United States.
³ Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States.

PMID: 30864791
DOI: 10.1021/acs.inorgchem.9b00107

Abstract

The iron(II)-nitroxyl complex [Fe(NO)(L3)] (1) (with L3^- = a hindered hydrotris(pyrazolyl)borate ligand), a high-spin (hs)-{FeNO}⁸ complex in the Enemark-Feltham notation, is surprisingly stable and is the first of its kind that could be structurally characterized. We further studied this compound using a variety of spectroscopic methods. These results indicate a hs iron(II) center with a bound ³NO^- ligand where the spins are antiferromagnetic coupled ( S_t = 1). Vibrational data show that this complex has a very strong Fe-NO bond. DFT calculations support this result and link it to very strong π-donation from the ³NO^- ligand to the iron(II) center. Furthermore, a very unusual equilibrium between the hs-{FeNO}⁸ complex and a dinitrosyl iron complex (DNIC) of {Fe(NO)₂}⁹ type is observed. The O₂ reactivity of the complex is finally reported.