Hydrogen bonding promotes diversity in nitrite coordination modes at a single iron(II) center

Abstract

A low-valent [FeN₅(OTf)₂] complex and its bisnitrite adduct, [FeN₅(NO₂)₂], have been synthesized in the interest of extending the reactivity of Fe complexes featuring redox-active ligands with secondary coordination sphere hydrogen-bond donors to nitrite reduction. Crystallographic characterization of [FeN₅(NO₂)₂] reveals that the nitrite ligands demonstrate both ɳ¹-NO₂ (N-nitro) and ɳ¹-ONO (O-nitrito) coordination modes. H-bonding between nitrite ligands and the protons on secondary amine moieties in the N₅ ligand play a pivotal role in positioning the nitrite ligands in multiple coordination modes. These results provide insights into the role of H-bonding in supporting disparate coordination modes of this substrate that can be translated to mechanisms of nitrite reduction in biological systems.

Graphical Abstract

Keywords:

• Nitrite
• iron
• redox-active ligand
• hydrogen bonding
• coordination chemistry

Acknowledgement

The authors would like to acknowledge Dr. Banu Kandemir for helpful conversations related to the electrochemistry of the complexes reported in this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

E. M. M. is a recipient of a Sloan Fellowship from the Alfred P. Sloan Foundation that has financially supported this research. K. L. B. acknowledges support from the University of Rochester.