organometallic compound
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What is an organometallic compound?
An organometallic compound contains at least one metal-to-carbon bond, where the carbon is part of an organic group. These compounds are used as catalysts and intermediates in both laboratory and industrial settings and have played a significant role in the science of chemistry.
Organometallic compounds are categorized based on the metal as either main-group compounds or transition metal compounds. Their physical and chemical properties vary greatly; for example, some are solids, liquids, or gases, and their heat and oxidation stability differ. The properties of these compounds depend on the type of carbon-metal bonds involved, which can be covalent, multicentre covalent, or ionic.
The first synthesized organometallic compound was Zeise’s salt, K[PtCl3(C2H4)], prepared in 1827 by William C. Zeise.
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What makes organometallic compounds different from other chemical compounds?
Organometallic compounds are unique because they contain at least one metal-to-carbon bond, where the carbon is part of an organic group. The "metal" can be a true metal such as lithium, magnesium, aluminum, or iron, or a metalloid like boron, silicon, germanium, or arsenic.
Most elements can be included as the metal in an organometallic compound, except for nitrogen and phosphorus in group 15, and all elements in groups 16, 17, and 18.
These compounds are used as catalysts and intermediates in both laboratory and industrial settings. The physical and chemical properties of organometallic compounds differ significantly, impacting their heat, stability, and reactivity.
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What elements are commonly found in organometallic compounds?
Organometallic compounds contain at least one metal-to-carbon bond, where the carbon is part of an organic group. These compounds are categorized based on the metal component, either as main-group compounds (groups 1, 2, and 13–15) or transition metal compounds (groups 3–12).
The carbon-metal bonds can be covalent, multicentre covalent, or ionic. Where covalent, the electrons are typically shared unequally, resulting in a polarized bond.
Common elements in organometallic compounds:
* Magnesium, used in Grignard reagents, is important in synthetic organic chemistry.
* Lithium and boron, also used in synthetic organic chemistry.
* Aluminum, employed in organic synthesis and, with titanium salts, as catalysts in the polymerization of unsaturated hydrocarbons.
* Lead, tin and mercury, are all commercially significant.
* Carbon monoxide, reacts with many transition-metal atoms to form metal carbonyls.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How are organometallic compounds made?
Organometallic compounds, crucial in chemical synthesis, can be synthesized through several methods.
- Hydrometallation The addition of a metal hydride to a multiple bond forms a metal-carbon bond.
- Grignard reagents Alkyl halides can be converted to organomagnesium halides, known as Grignard reagents, by reduction with magnesium.
- Direct combination A metal ion and ligands combine directly in solution.
- Redistribution reactions Double displacements involving the same central element.
These methods facilitate the creation of diverse organometallic compounds with varied applications.
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What are some uses of organometallic compounds in industry or daily life?
Organometallic compounds are substances with a metal-to-carbon bond, where the carbon is part of an organic group. They are widely used as catalysts and intermediates in both laboratory and industrial settings to speed up reactions without being consumed themselves.
Examples of uses:
* Grignard reagents: Organomagnesium halides are used in synthetic organic chemistry, as are organolithium and organoboron compounds.
* Catalysts: Alkylaluminum compounds, when combined with titanium salts, catalyze the polymerization of unsaturated hydrocarbons like ethylene and propylene. Metal carbonyls are also employed as catalysts in the petrochemical industry.
* Commercial applications: Organotin compounds are used as pharmaceuticals, pesticides, stabilizers for polyvinyl chloride, and fire retardants.
* Purification: Tetracarbonylnickel, a volatile nickel compound, was the basis for purifying nickel.1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why are organometallic compounds important in modern chemistry?
Organometallic compounds are important in modern chemistry because they act as catalysts and intermediates in both laboratory and industrial settings. Grignard reagents, organolithium, and organoboron compounds are used in synthetic organic chemistry. Alkylaluminum compounds, along with titanium salts, catalyze the polymerization of unsaturated hydrocarbons like ethylene and propylene.
Organometallic compounds containing lead, tin, and mercury have commercial value. Many organotin compounds are used as stabilizers for polyvinyl chloride, pharmaceuticals, pesticides, and fire retardants. Metal carbonyls are also employed as catalysts in reactions within the petrochemical industry.
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organometallic compound, any member of a class of substances containing at least one metal-to-carbon bond in which the carbon is part of an organic group. Organometallic compounds constitute a very large group of substances that have played a major role in the development of the science of chemistry. They are used to a large extent as catalysts (substances that increase the rate of reactions without themselves being consumed) and as intermediates in the laboratory and in industry. The class includes such compounds as ferrocene, a remarkably stable compound in which an iron atom is sandwiched between two hydrocarbon rings.
Organometallic compounds are typically discussed in terms of the metal as either main-group compounds or transition metal compounds. The main-group metals of organometallic compounds are typically considered to be those of the S-block (groups 1 and 2) and the heavier elements of the p-block (groups 13–15) in the periodic table of elements. The transition metals include those elements in the d- and f-blocks (groups 3–12).
The physical and chemical properties of organometallic compounds vary greatly. Most are solids, particularly those whose hydrocarbon groups are ring-shaped or aromatic, but some are liquids and some are gases. Their heat and oxidation stability vary widely. Some are very stable, but a number of compounds of electropositive elements such as lithium, sodium, and aluminum are spontaneously flammable. Many organometallic compounds are highly toxic, especially those that are volatile.
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The properties of the organometallic compounds depend in large measure on the type of carbon-metal bonds involved. Some are ordinary covalent bonds, in which pairs of electrons are shared between atoms. Others are multicentre covalent bonds, in which the bonding involves more than two atoms. A third type are ionic bonds, in which the bonding electron pair is donated by only one atom. In donor-acceptor bonds, the metal atom is connected to hydrocarbons with multiple bonds between carbon atoms.
Where metal atoms form covalent bonds with carbon atoms, the electrons are usually shared unequally. As a result, the bond is polarized—one end is more negative than the other. The extent of polarization depends on the strength with which the metal atom binds electrons. Organometallic compounds range in polar power from methylpotassium, in which the bond is almost like certain ionic bonds, to lead, which bonds with carbon with very little polarization.
Importance of organometallic compounds
Because of bond polarity, many organometallic compounds have reactivities that have made them important in chemical synthesis. The organomagnesium halides (Grignard reagents), for example, are used widely in synthetic organic chemistry, as are organolithium and organoboron compounds. Alkylaluminum compounds are also employed in organic synthesis. Used with titanium salts, they are important catalysts in the polymerization of unsaturated hydrocarbons, such as ethylene and propylene. The mechanism of action of the titanium-aluminum alkyl catalysts probably involves interaction between the titanium atoms and the double bonds of the hydrocarbons.
Organometallic compounds containing lead, tin, and mercury are all commercially significant. A large number of organotin compounds, for example, are used as pharmaceuticals, pesticides, stabilizers for polyvinyl chloride, and fire retardants. Methylmercury has caused severe pollution problems as a result of its toxicity. This fact has led to stringent controls on the discharge of mercury from chemical plants into rivers, lakes, and oceans.
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Carbon monoxide reacts readily with many transition-metal atoms to form metal carbonyls, themselves a class of organometallics. One of the earliest to be discovered was tetracarbonylnickel, a volatile nickel compound that became the basis of a process for purifying nickel. Metal carbonyls are employed as catalysts in many reactions in the petrochemical industry.