Organocadmium chemistry describes the physical properties, synthesis, reactions, and use of organocadmium compounds, which are

organometallic compound Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and ...

s containing a

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

chemical bond A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...

. Cadmium shares group 12 with

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

and mercury and their corresponding chemistries have much in common. The synthetic utility of organocadmium compounds is limited. The simplest organocadmium compound is

dimethylcadmium Dimethylcadmium is the organocadmium compound with the formula . It is a colorless, highly toxic liquid that fumes in air. It is a linear molecule with C-Cd bond lengths of 213 pm. The compound finds limited use as a reagent in organic synthesi ...

. It is a linear molecule with a C-Cd

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

of 213 pm. Organocadmium compounds are typically sensitive to air, light, and moisture.

Synthesis

Dimethylcadmium and diethylcadmium were reported in 1917 by Erich Krause. In general, they are prepared by transmetalation or by an exchange reaction between an alkylating agent and a cadmium salt. According to one procedure, diethylcadmium is produced by the reaction of cadmium bromide with two equivalents of the

Grignard reagent Grignard reagents or Grignard compounds are chemical compounds with the general formula , where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride and phenylmagnesium bromi ...

ethylmagnesium bromide in

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

. Diethylcadmium is a colorless oil with

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

−21 °C. Diphenylcadmium can be prepared by the reaction of

phenyllithium Phenyllithium is an organometallic agent with the empirical formula . 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. Crystalline phenyl ...

with cadmium bromide. Diphenylcadmium is a solid with a melting point of 174 °C.

Fluoroalkyl and alkenyl derivatives

Following established trends, perfluorinated alkyl and alkenyl derivatives of cadmium exhibit improved thermal stability. The alkenyl derivatives are generated by the addition of iodotrifluoroethylene to cadmium metal.

Reactions

Organocadmium compounds are less nucleophilic than the organozincs. This reduced reactivity is demonstrated in the conversion of

acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s to

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

s with these reagents. This reaction was reported by Henry Gilman in 1936 and was used until less toxic cuprates were available. The related Grignard reagent would react further, giving to the tertiary

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

. Methyl cadmium was used in one of the steps leading to

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 (organic chemist), Robert Robinson with John Cor ...

: :

Organocadmium chemistry cholesterol synthesis Woodward

Another 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

group or the

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

group. This selectivity is observed provided that the reaction is carried out salt free. When the cadmium reagent is generated

in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...

from a cadmium salt, the halide generates a more nucleophilic organocadmium reagent, an ate complex. The same salt effect can be observed with organozinc compounds. Dimethylcadmium has been used to synthesize colloidal nanocrystals of II-VI materials such as

cadmium selenide Cadmium selenide is an inorganic compound with the formula Cd Se. It is a black to red-black solid that is classified as a II-VI semiconductor of the n-type. It is a pigment, but applications are declining because of environmental concerns. ...

. Its toxic and volatile nature has led researchers to look elsewhere for cadmium precursors such as cadmium oxide.

Toxicity

Cadmium compounds are toxic. Dimethylcadmium is toxic to the kidney, the liver, the central nervous system, and the respiratory organs when inhaled. Cadmium compounds in general are considered to be

carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

to humans by the IARC.

References

{{ChemicalBondsToCarbon Organometallic compounds Cadmium compounds