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5-ish Slides about Enemark-Feltham Notation

5-ish Slides about Enemark-Feltham Notation. Kyle Grice DePaul University November 2018. Iron Nitrosyl Complexes. NO ligands are redox non-innocent , which means NO has multiple accessible redox states under common conditions

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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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