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5-ish Slides about Enemark-Feltham Notation

Delve into the basics, bond characteristics, and implications of Enemark-Feltham Notation in Iron Nitrosyl Complexes, uncovering the nuances of redox states and structural features. Discover the significance of NO ligands and their role in defining the chemistry of these compounds. Learn about research on NO-releasing molecules for medical applications.

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5-ish Slides about Enemark-Feltham Notation

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  1. 5-ish Slides about Enemark-Feltham Notation Kyle Grice DePaul University November 2018

  2. Iron Nitrosyl Complexes • NO ligands are redoxnon-innocent, which means NO has multiple accessible redox states under common conditions • In addition, Iron has common several redox and spin-states (Fe2+vs. Fe3+, high spin or low spin).

  3. NO (Yes?) • As a neutral molecule, NO is a radical with one unpaired electron • NO has been found to be a neurotransmitter and vasodialator • There has been significant research in NO-releasing molecules (NORMs) for medical applications. Bond Order: 2.5 Bond Length: 115 pm

  4. Basics of Enemark-Feltham • {M-L}X or {Fe-NO}X where X is the sum of the metal valence and ligand π* electrons. • NO+ has no π* electrons, NO has 1, and NO- has 2. • Iron can be high spin or low spin in several oxidation states! • Nitroprusside is a blood-pressure lowering compound: • Enemark-Feltham Notation: {Fe-NO}6

  5. How do we get more detailed info? • Often it is hard to determine the exact oxidation state. • information can sometimes be obtained from the NO ligand: • NO+ ligands have shorter bonds because they have formally triple N-O bonds. They tend to be linear. • NO- are bent due to the extra lone pair on the nitrogen. • NO is in-between these two extremes in term s of length and angle • IR frequencies also help: Linear: 1650 – 1900 cm-1 Bent: 1520 – 1690 cm-1 • Linear Fe-N-O bonding and a short N-O distance. The molecule is diamagnetic too! • This is low spin Fe2+ with a NO+ ligand.

  6. Beyond Enemark-Feltham • To deconvolute the oxidation state of the iron and the NO, various methods can be used: • Evidence from X-ray structures and IR • DFT calculations • Fe K-edge XAS • Fe Mossbauer

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