chelate compound

Examples of chelate compound in the following topics:

• Chelating Agents

  • Usually these ligands are organic compounds and are called chelants, chelators, chelating agents, or sequestering agents; the resulting complexes are called chelate compounds.
  • Chelating agents, unlike the other ligands in coordination compounds, bind via multiple atoms in the ligand molecule, not just one.
  • Chelation results in the formation of a five-membered ring.
  • Organic compounds such as the amino acids glutamic acid and histidine, organic diacids such as malate, and polypeptides such as phytochelatin are also typical chelators.
  • Enterobactin, produced by E. coli, is the strongest chelating agent known.

• Siderophores

  • Siderophores are classified by which ligands they use to chelate the ferric iron, including the catecholates, hydroxamates, and carboxylates.
  • Siderophores are small, high-affinity iron chelating compounds secreted by microorganisms such as bacteria, fungi, and grasses.
  • Because of this property, they have attracted interest from medical science in metal chelation therapy, with the siderophore desferrioxamine B gaining widespread use in treatments for iron poisoning and thalassemia.
  • The most effective siderophores are those that have three bidentate ligands per molecule, forming a hexadentate complex and causing a smaller entropic change than that caused by chelating a single ferric ion with separate ligands.
  • Siderophores are usually classified by the ligands used to chelate the ferric iron.

• Reactions of Coordination Compounds

  • Many metal-containing compounds consist of coordination complexes.
  • These complexes are called chelate complexes, the formation of which is called chelation, complexation, and coordination.

• Sulfur Compounds

  • Sulfur forms stable compounds with most elements except the noble gases.
  • Sulfur forms stable compounds with all elements except the noble gases.
  • For some organic sulfur compounds, smell depends on their concentration.
  • An important S–N compound is the cage tetrasulfur tetranitride (S4N4).
  • Thiols or mercaptans (as they are mercury capturers as chelators) are the sulfur analogs of alcohols; treatment of thiols with base gives thiolate ions.

• Models for Addition to Acyclic Substrates

  • As expected, the behavior of conformationally mobile acyclic compounds is more difficult to rationalize.
  • Because of the conformational mobility of these compounds, it is important to recognize an important precept known as The Curtin-Hammett Principle.
  • The silyl ether derivative in example 9 is a case of steric hindrance to chelation.
  • The chelation model leads to a similar prediction.
  • The absence of a chelating metal combined with the bulk of the hydride donor results in a >95 %de, despite the replacement of chlorine by the much stronger chelating ligands (CH3)2N- and CH3CO2-.

• Copper

  • The simplest compounds of copper are binary compounds, i.e. those containing only two elements.
  • The principal compounds are the oxides, sulfides, and halides.
  • The simplest compounds of copper are binary compounds (i.e., those containing only two elements).
  • The principal compounds are the oxides, sulfides, and halides.
  • Amino acids form very stable chelate complexes with copper(II).

• Isomers in Coordination Compounds

  • As with other compounds, there are several kinds of coordination complex isomers.
  • Isomers are distinct compounds that can have different physical properties such as color, crystal structure, and melting point.

• Enantioselective Aldol Reactions

  • Although the enolborinate by itself might be expected to exist in a chelated form, with two B–O bonds, the aldol reaction requires a reorganization of this chelation in order to activate the aldehyde carbonyl group for nucleophilic addition.
  • As shown by the formula in brackets, the free oxazolidinone ring has rotated 180º from its chelated position in order to minimize dipole repulsion.
  • If the auxiliary remains chelated to the enolate during the aldol reaction the stereochemical outcome is changed.
  • In the upper equation a chelated Z-titanium enolate is initially formed and then reacted with an aldehyde.
  • The change in selectivity relative to the siloxy substituent is due to its chelation effect in the lithium enolate and non-chelated polar effect in the boron enolate.

• Allyl and Crotyl Addition to Aldehydes and Ketones

  • Because of its potential usefulness in synthesis, organic chemists have sought ways to achieve predictable control of diastereoselectivity in the addition of methallyl groups to carbonyl compounds via crotyl reagents.
  • The stereoisomers of these compounds are not only configurationally stable at room temperature, but the compounds themselves are tolerant of exposure to air and moisture, making their preparation storage and use relatively simple.
  • Because the allyl addition proceeds by a cyclic transition state incorporating a tetra-coordinate boron atom, the chelation model is not an option, and a non-chelation transition state accommodating the polarity of the substituent provides the best explanation.

• Simple and Compound Sentences