An organocadmium compound is an

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 so ...

containing a

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

chemical bond A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing o ...

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

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc 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 t ...

and mercury and their corresponding chemistries have much in common. The synthetic utility of organocadmium compounds is limited. The simplest organocadmium compound is dimethylcadmium. 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 nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest ...

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 Transmetalation (alt. spelling: transmetallation) is a type of organometallic reaction that involves the transfer of ligands from one metal to another. It has the general form: :M1–R + M2–R′ → M1–R′ + M2–R where R and R′ can be, but ...

or by an exchange reaction between an alkylating agent and a cadmium salt. According to one procedure, diethylcadmium is produced the reaction of

cadmium bromide Cadmium bromide is the inorganic compound with the formula CdBr2. It is a white hygroscopic solid. It also can be obtained as a mono- and tetrahydrate. It has few applications. Preparation Cadmium bromide is prepared by heating cadmium with bro ...

with two equivalents of the Grignard reagent ethylmagnesium bromide in

diethyl ether Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liq ...

. 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 from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

−21

°C The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The d ...

. Diphenylcadmium can be prepared by the reaction of

phenyllithium Phenyllithium or lithobenzene 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 synth ...

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 Iodotrifluoroethylene is the organofluorine compound with the formula . It is a volatile colorless liquid. Preparation and reactions It is prepared by iodination of trifluorovinyl lithium. Iodotrifluoroethylene reacts with cadmium metal to giv ...

to cadmium metal.

Reactions

Organocadmium compounds are less

nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...

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 ...

s to

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

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 most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

. Methyl cadmium was used in one of the steps leading to cholesterol total synthesis: : 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 oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

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

in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...

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. 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 substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subst ...

to humans by the IARC.

References

{{ChemicalBondsToCarbon Organometallic compounds Cadmium compounds