Organometallic chemistry

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Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Often this definition is too strict however, since many compounds without such bonds are chemically similar. An appropriate alternative may be "compounds containing metal-element bonds of a largely covalent character". Organometallic chemistry combines aspects of inorganic chemistry and organic chemistry. Organometallic compounds are also known as Organo-Inorganics, Metallo-Organics and Metalorganics. Organometallic compounds are distinguished by the prefix "organo-".

Examples

Some typical organometallic compounds are

• organozinc compounds such as ClZnCH₂C(=O)OEt (chloro(ethoxycarbonylmethyl)zinc),
• organocuprates such as Li[CuMe₂] (lithium dimethylcuprate),
• organomagnesium compounds such as the Grignard reagents MeMgI (methylmagnesium iodide) and MgEt₂ (diethylmagnesium), and
• organolithium compounds such as n-butyllithium
• organotransition metal compounds such as Ferrocene
• organopalladium compounds
• Agostic complexes where hydrocarbons and H₂ serve as ligands.

Important classes of organometallic compounds are metal carbonyls, metallocenes (with ferrocene as a prime example), and carbene complexes. The term "metal" is defined deliberately broadly in this context and may include elements, such as silicon, arsenic or boron, which are not metallic but are considered to be metalloids such as the organoborane triethylborane (Et₃B ) or the organosilicon compound tetramethylsilane (Me₄Si, TMS). There is also the group of poor metal elements such as aluminium that form organoaluminiums, and aluminoxanes which are important parts of Ziegler-Natta catalysts.

Use and concepts

Organometallic compounds often find practical use in stoichiometric and catalytically active compounds, for example in the processing of petroleum products and the production of polymers.

The 18-Electron rule and the isolobal principle are concepts that help to understand chemical bonding and reactivity in organometallic compounds.

Key reaction mechanisms are oxidative addition, reductive elimination, transmetalation, electron transfer, beta-hydride elimination and organometallic substitution reactions.

History

Early developments: Cadet’s synthesis of methyl arsenic compounds related to the cacodylic acid, Zeise's platinum-ethylene complex, Edward Frankland’s discovery of dimethyl zinc, Ludwig Mond’s discovery of Ni(CO)₄, and Victor Grignard’s organomagnesium compounds. The abundant and diverse products from coal and petroleum led to Ziegler-Natta, Fischer-Tropsch, hydroformylation catalysis which employ CO, H₂, and alkenes as feedstocks and ligands. Recognition of organometallic chemistry as a distinct subfield culminated in the Nobel Prizes to Fischer and Wilkinson for work on metallocenes. In 2005, Chauvin, Grubbs, and Schrock shared the Nobel Prize for metal-catalyzed alkene metathesis.

Organometallic chemistry timeline

• 1760 Louis Claude Cadet de Gassicourt investigates inks based on Cobalt salts and isolates Cacodyl from cobalt mineral containing arsenic
• 1827 Zeise's salt is the first platinum / olefin complex
• 1863 Charles Friedel and James Crafts prepare organochlorosilanes
• 1890 Ludwig Mond discovers Nickel carbonyl
• 1899 Introduction of Grignard reaction
• 1900 Paul Sabatier works on hydrogenation organic compounds with metal catalysts. Hydrogenation of fats kicks off advances in food industry, see margarine
• 1912 Nobel Prize Victor Grignard and Paul Sabatier
• 1930 Henry Gilman works on lithium cuprates, see Gilman reagent
• 1963 Nobel prize for Karl Ziegler and Giulio Natta on Ziegler-Natta catalyst
• 1965 Discovery of cyclobutadieneiron tricarbonyl
• 1968 Heck reaction
• 1973 Nobel prize Geoffrey Wilkinson and Ernst Otto Fischer on sandwich compounds
• 2005 Nobel prize Yves Chauvin, Robert Grubbs, and Richard Schrock on metal-catalyzed alkene metathesis

Organometallics

• Period 2 elements: organolithium chemistry, organoberyllium chemistry, organoborane chemistry,
• Period 3 elements: organomagnesium chemistry, organoaluminum chemistry, organosilicon chemistry
• Period 4 elements: organotitanium chemistry,organochromium chemistry, organomanganese chemistry organoiron chemistry, organocobalt chemistry organonickel chemistry, organocopper chemistry, organozinc chemistry, organogallium chemistry, organogermanium chemistry
• Period 5 elements: organopalladium chemistry, organosilver chemistry, organocadmium chemistry, organoindium chemistry, organotin chemistry
• Period 6 elements: organoplatinum chemistry, organogold chemistry, organomercury chemistry,organothallium chemistry, organolead chemistry

See also

• Chelation
• Bioorganometallic chemistry

External links

• MIT OpenCourseWare: Organometallic Chemistry

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