Organocadmium compound - AbsoluteAstronomy.com

An organocadmium compound is a organometallic compound 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 cadmium

Cadmium

Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

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...

. Organocadmium chemistry describes physical properties, synthesis, reactions and use of these compounds. Cadmium shares group 12

Group 12 element

A group 12 element is one of the elements in group 12 in the periodic table. This includes zinc , cadmium and mercury . The further inclusion of copernicium in group 12 is supported by recent experiments on individual Cn atoms...

with zinc

Zinc

Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

and mercury

Mercury (element)

Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

and their corresponding chemistries have much in common.

Dimethylcadmium is a linear molecule with C-Cd bond length

Bond length

- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...

s of 211.2 pm. All organocadmiums are sensitive to air, light and moisture.

Synthesis

The first organocadmium compounds, dimethylcadmium, CH₃-Cd-CH₃ and diethylcadmium CH₃CH₂-Cd-CH₂CH₃ were prepared in 1917 by Erich Krause. In general they are prepared by transmetalation

Transmetalation

Transmetalation is a general chemical reaction type in organometallic chemistry describing the exchange of ligands between two metal centers....

or by an exchange reaction between an organometallic reagent and a cadmium salt.

One procedure for synthesis diethylcadmium is by reaction of cadmium bromide

Cadmium bromide

Cadmium bromide is a cream-coloured crystalline ionic cadmium salt of hydrobromic acid that is soluble in water. It is very toxic, along with other cadmium compounds.-Uses:It is used in the manufacturing of photographic film, engraving and lithography....

with two equivalents of the Grignard reagent ethylmagnesium bromide in diethyl ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

. A byproduct is magnesium bromide

Magnesium bromide

Magnesium bromide is a chemical compound of magnesium and bromine that is white and deliquescent. It is often used as a mild sedative and as an anticonvulsant for treatment of nervous disorders. It is water soluble and somewhat soluble in alcohol...

. Diethylcadmium is a colorless oil with melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

−21 °C.

Diphenylcadmium can be prepared by reaction of phenyllithium

Phenyllithium

Phenyllithium is an organometallic agent with the empirical formula C6H5Li. It is most commonly used as a metalating agent in organic syntheses and a substitute for Grignard reagents for introducing phenyl groups in organic syntheses...

with the same salt . This solid has a melting point of 174 °C

Reactions

The synthetic utility of organocadmiums is limited. The alkyl groups in them are less nucleophilic than the organozincs due to the general increase in electronegativity

Electronegativity

Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...

going down group 12. this reduced reactivity is demonstrated in the conversion of acid chlorides to ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

s with these reagents. This reaction was discovered by Henry Gilman

Henry Gilman

Henry Gilman was an American organic chemist known as the father of organometallic chemistry, the field within which his most notable work was done. He discovered the Gilman reagent, which bears his name....

in 1936 and was used until less toxic cuprates were available. With other organometallic reagents such reaction would continue to the corresponding alcohol

Alcohol

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

.

An example of the synthetic use of an organocadmium is the reaction of diisoamylcadmium with β-carbomethoxypropionyl chloride to methyl 4-keto-7-methyloctanoate without reacting further with the ketone

Ketone

group or the ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

group.

Another example is the use of methyl cadmium in one of the steps leading to cholesterol total synthesis

Cholesterol total synthesis

Cholesterol total synthesis in chemistry describes the total synthesis of the complex biomolecule cholesterol and is considered a great scientific achievement. . The research group of Robert Robinson with John Cornforth published their synthesis in 1951 and that of of Robert Burns Woodward with...

:
Dimethylcadmium is also used in the synthesis of colloidal nanocrystals although its toxic and volatile nature has led researchers to look elsewhere for cadmium precursors such as cadmium oxide.

This selectivity exists provided that the reaction is carried out salt free. When the cadmium reagent is generated in situ

In situ

In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...

from a cadmium salt, the presence of a halide salt makes the reagent much more reactive, even to ketones. the same salt effect can be observed in organozinc compounds.

Synthesis

Reactions

See also