Organoantimony chemistry
Encyclopedia
Organoantimony chemistry is the chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

 of compounds
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 containing a carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 to antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

 (Sb) chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...

. Relevant oxidation states are Sb(V) and Sb(III). The toxicity of antimony limits practical application in organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

.

Organoantimony(V) chemistry

Antimony compounds of the type R5Sb (stiboranes) can be synthesised from trivalent Sb precursors:
Ph3Sb + Cl2 → Ph3SbCl2
Ph3SbCl2 + 2 PhLi → Ph5Sb


Asymmetric compounds can also be obtained through the stibonium ion:
R5Sb + X2 → [R4Sb]+[X]
[R4Sb]+[X] + R'MgX → R4R'Sb


Just as in the related organobismuth compounds (same group 15), organoantimony(V) compounds form onium compounds and ate complex
Ate complex
An ate complex in chemistry is a salt formed by reaction of a Lewis acid with a base whereby the central atom increases its valence . Often in chemical nomenclature the phrase ate is suffixed to the element in question. For example, the ate complex of a boron compound is called a borate...

es.

Pentaphenylantimony decomposes at 200 °C to triphenylstibine
Triphenylstibine
Triphenylstibine is the chemical compound with the formula Sb3. Abbreviated SbPh3, this colourless solid is often considered the prototypical organoantimony compound...

 and biphenyl
Biphenyl
Biphenyl is an organic compound that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula 2...

. It forms a trigonal bipyramidal molecular geometry. In the related Me5Sb all methyl protons are equivalent at -100 °C in proton NMR
Proton NMR
Proton NMR is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure of its molecules. In samples where natural hydrogen is used, practically all of the hydrogen consists of the...

. Compounds of the type R4SbX tend to form dimers.

Organoantimony(III) chemistry

Compounds of the type R3Sb (stibines) can be accessed by reaction of antimony trichloride
Antimony trichloride
Antimony trichloride is the chemical compound with the formula SbCl3. The soft colorless solid with a pungent odor was known to the alchemists as butter of antimony.-Preparation:...

 with organolithium compounds or Grignard
Grignard
Grignard can be a French last name, or refers to an organic chemical reaction.* Victor Grignard, a French organic chemist.* The Grignard Company a chemical manufacturer.* Grignard reaction, an organic chemical reaction developed by Victor Grignard....

s.
SbCl3 + 3 RLi (or RMgCl) → R3Sb


Typical reactions are:
R3Sb + Br2 → R3SbBr2
R3Sb + O2 → R3SbO
R3Sb + Na + NH3 → R2SbNa
R3Sb + B2H6 → R3Sb.BH3


Stibanes are weak Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...

s and therefore ate complexes are not encountered. On the other hand they have good donor properties and are therefore widely used in coordination chemistry. R3Sb compounds are more air-sensitive than the R5Sb counterparts.

Antimony Metallocene
Metallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride...

s are known as well:
14SbI3 + 3 (Cp*Al)4 → [2Cp*Sb]+[AlI4]- + 8Sb + 6 AlI3

The Cp*-Sb-Cp* angle is 154°.

The cyclic compound stibole
Stibole
Stibole is a theoretical heterocyclic organic compound, a five-membered ring with the formula C4H4SbH. It is classified as a metallole. It can be viewed as an structural analog of pyrrole, with antimony replacing the nitrogen atom of pyrrole...

, a structural analog of pyrrole
Pyrrole
Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. It is a colourless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3...

, has not been isolated, but substituted derivatives known as stiboles are known.

Organoantimony(II) chemistry

Distibines have a Sb-Sb single bond and are of some interest as thermochromic materials. For example tetramethyldistibine is a colorless as a gas, yellow as a liquid, red as solid just below the melting point of 18.5 °C and again yellow well below the melting point.

See also

  • Chemical bonds of carbon with other elements in the periodic table:

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