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Related Concept Videos

Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

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In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
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Metal-Ligand Bonds02:51

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The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
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Complexation Equilibria: Factors Influencing Stability of Complexes01:09

Complexation Equilibria: Factors Influencing Stability of Complexes

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In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
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Radical Formation: Homolysis00:54

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A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up by one atom forming ions by the cleavage called heterolysis, or the two electrons are shared by two atoms, with one each creating radicals by the cleavage called homolysis.
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Radical Reactivity: Overview01:11

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2.1K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
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EDTA: Chemistry and Properties01:22

EDTA: Chemistry and Properties

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Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
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Accessing Unusual Reactivity through Chelation-Promoted Bond Weakening.

Nicholas G Boekell1, Caroline O Bartulovich1, Sandeepan Maity2

  • 1Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States.

Inorganic Chemistry
|March 13, 2023
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Summary
This summary is machine-generated.

A new samarium dibromide N-methylethanolamine (SmBr2-NMEA) reagent system enables potent proton-coupled electron transfer (PCET) reductions. This powerful reductant effectively reduces challenging substrates, including those relevant to nitrogen fixation.

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Area of Science:

  • Organometallic Chemistry
  • Synthetic Chemistry
  • Redox Chemistry

Background:

  • Proton-coupled electron transfer (PCET) is crucial for many chemical transformations.
  • Developing potent PCET reductants requires understanding metal-ligand interactions and X-H bond weakening.
  • Low-valent metal reductants offer unique reactivity profiles.

Purpose of the Study:

  • To investigate the relationship between low-valent metal-protic ligand affinity and X-H bond weakening.
  • To develop potent proton-coupled electron transfer (PCET) reductants.
  • To explore the reactivity of samarium(II) complexes with protic ligands.

Main Methods:

  • Systematic investigation of various samarium(II)-protic ligand reductant systems.
  • Characterization of metal-ligand affinity and stability against H2 evolution.
  • Testing the reductive capabilities of the optimized SmBr2-NMEA system on diverse substrates.

Main Results:

  • Samarium dibromide N-methylethanolamine (SmBr2-NMEA) demonstrated superior metal-ligand affinity and stability.
  • SmBr2-NMEA effectively reduced recalcitrant substrates like alkynes, lactones, and arenes.
  • NMEA's chelating role enabled unique reductive cyclizations, and the system reduced nitrogen fixation intermediates.

Conclusions:

  • SmBr2-NMEA is a powerful and versatile reductant for challenging organic transformations.
  • The study highlights the potential for rational design of PCET reagents with weakened X-H bonds.
  • This work advances the development of novel synthetic methodologies using low-valent metal reductants.