Everything about Organometallic Chemistry totally explained
Organometallic chemistry is the study of
chemical compounds containing
bonds between
carbon and a
metal. Since many compounds without such bonds are chemically similar, an 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
Organometallic compounds are also known as organo-inorganics, metallo-organics and
metalorganics. Organometallic compounds are distinguished by the prefix "organo-" for example organopalladium compounds. Examples of such organometallic compounds include all
Gilman and
Grignard reagents which contain
lithium and
copper, and
magnesium respectively.
Tetracarbonyl nickel, and
ferrocene are examples of organometallic compounds containing
transition metals.
In addition to the traditional metals and semimetals, elements such as
boron,
silicon,
arsenic, and
selenium are considered to form organometallic compounds. Examples include organomagnesium compounds such as iodo(methyl)magnesium MeMgI, diethylmagnesium (Et
2Mg); organolithium compounds such as butyllithium (BuLi), organozinc compounds such as chloro(ethoxycarbonylmethyl)zinc (ClZnCH
2C(=O)OEt); organocopper compounds such as lithium dimethylcuprate (Li
+[CuMe
2]
–); and organoborane compounds such as triethylborane (Et
3B).
Many organometallic compounds exist in biological systems. For example,
hemoglobin and
myoglobin contain an
iron center bonded to a
porphyrin ring;
magnesium is the center of a
chlorin ring in
chlorophyll. The specialized field of such
inorganic compounds is known as
bioinorganic chemistry.
Structure and properties
The status of compounds in which the canonical anion has a delocalized structure in which the negative charge is shared with an atom more electronegative than carbon, as in enolates, may vary with the nature of the anionic moiety, the metal ion, and possibly the medium; in the absence of direct structural evidence for a carbon–metal bond, such compounds are not considered to be organometallic.
Depending mostly on the nature of metallic ion and somewhat on the nature of the
organic compound, the character of the bond may either be ionic or covalent. Organic compounds bonded to sodium or potassium are primarily ionic. Those bonded to lead, tin, mercury, etc. are considered to have
covalent bonds, and those bonded to magnesium or lithium have bonds with intermediate properties.
Organometallic compounds with bonds that have characters in between ionic and covalent are very important in industry, as they're both relatively stable in solutions and relatively ionic to undergo reactions. Two important classes are
organolithium and
Grignard reagents. In certain organometallic compounds such as
ferrocene or dibenzenechromium, the
pi orbitals of the organic moiety ligate the metal.
Applications
Organometallic compounds find practical use in
stoichiometric and
catalytically active compounds.
Tetraethyl lead previously was combined with
gasoline as an
antiknock agent. Due to lead's toxicity it's no longer used, its replacements being other organometallic compounds such as
ferrocene and
methylcyclopentadienyl manganese tricarbonyl (MMT).The Monsanto process utilizes a rhodium-carbonyl complex to manufacture acetic acid from methanol and carbon monoxide industrially. The Ziegler-Natta catalyst is a titanium-based organometallic compound used in the production of polyethylene and other polymers.
Ryoji Noyori's chiral
ruthenium-
BINAP complex catalytically reduces beta-ketoesters to secondary alcohols in the production of
fine chemicals and
pharmaceuticals. Another catalyst is the
Grubbs catalyst, a
carbenoid (an organometallic compound of a
carbene and a metal).
Concepts
Electron counting is key in understanding organometallic chemistry. The
18-electron rule is helpful in predicting the stabilities of organometallic compounds. Organometallic compounds which have 18 electrons (filled s, p, and penultimate d orbitals) are relatively stable. This suggests the compound is isolable, but it can result in the compound being inert.
To understand chemical bonding and reactivity in organometallic compounds the
isolobal principle should be used.
NMR and
infrared spectroscopy are common techniques used to determine structure and bonding in this field. Scientists are allowed to probe fluxional behaviors of compounds with variable-temperature NMR.
Organometallic compounds undergo several important reactions:
History
Early developments in organometallic chemistry include
Louis Claude Cadet’s synthesis of methyl arsenic compounds related to
cacodyl,
William Christopher 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, H
2, and alkenes as feedstocks and ligands.
Recognition of organometallic chemistry as a distinct subfield culminated in the Nobel Prizes to
Ernst Fischer and
Geoffrey Wilkinson for work on
metallocenes. In 2005,
Yves Chauvin,
Robert H. Grubbs and
Richard R. Schrock shared the Nobel Prize for metal-catalyzed
olefin 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
1909 Paul Ehrlich introduces Salvarsan for the treatment of syphilis, an early arsenic based organometallic compound
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 chemistryFurther Information
Get more info on 'Organometallic Chemistry'.
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