Organometallic chemistry
Organometallic Chemistry in the original definition of the chemical compounds in which an organic group or an organic compound is bonded directly to a metal atom. These compounds ( organylmetal or organometallic compounds ) are referred to as metal-organic or organometallic compounds. Today, the term is also generally passed on. It also includes derivatives of such elements to the organometallic compounds which, although in the elemental state do not form a metal, but a low electronegativity have such as silicon or boron It is better but in these cases of element-organic compounds ( Elementorganyle ) to speak.
Thus, metal organyls or element containing at least one carbon atom and at least one metal or electro- positive element atom (s ) which are bonded to each other. EC- bond is a more or less polar covalent bond. The organyl can be attached via either a single, double or even triple bond to the element, or be associated in several ways with the element atom as in ferrocene ( see below). Not, however, to the organometallic compounds include the carbides, steel is, for example, in spite of its carbon content of an alloy and not a metal- organic compound.
Substances such as sodium acetate ( H3C - COONa, the sodium salt of acetic acid) are also included in spite of the metal ion and the existing Organylrestes ( methyl, H3C ), not to the metal- organic compounds. This fact has no direct Na - C bond. Instead, the acetate group is predominantly ionically bonded through its oxygen atoms to the sodium ion. Also, chlorophyll and hemoglobin are by this definition no organometallic compounds, since in them the central magnesium or iron atom of nitrogen atoms is coordinated.
History
One of the early discoveries in organometallic chemistry include Louis Claude Cadet synthesis of related with cacodyl methyl arsenic compounds, William Christopher Zeise platinum -ethylene complex, Edward Frankland's discovery of Dimethylzinks and Ludwig moon discovery of Nickeltetracarbonyls. Significantly for organic synthesis are the Grignard reagents, which are magnesium organyls, which are abbreviated as RMgX. They were discovered by Victor Grignard, who received it with Paul Sabatier in 1912 the Nobel Prize.
On an industrial scale were Ziegler -Natta catalysts, Fischer-Tropsch catalysts and other organometallic complexes are used in processes such as the hydroformylation, using carbon monoxide, hydrogen and olefins as feedstocks, and ligands. For the discovery of organometallic catalysts for the production of plastics were Karl Ziegler and Giulio Natta in 1963 the Nobel Prize.
In the 20th century, the tetraethyl lead PbEt4 was the most produced organometallic compound, which was added to petrol to improve resistance. Due to their highly toxic and catalyst-damaging effect of such additives since the 1980s, however, found less and less use. And there were studied as its substitute other organometallic compounds such as ferrocene and Tricarbonylmethylcyclopentadienylmangan (MMT ), but found this no large-scale deployment. Also because of harmful side effects are controversial, the organotin compounds such as tributyltin, which are used as stabilizers in plastics and for the protection of ship hulls.
A major boost for the organometallic chemistry, has promoted the establishment as an independent discipline, brought the discovery of ferrocene ( dicyclopentadienyl, C5H5 -Fe -C5H5 ) 1951. Recognition and significance of organometallic chemistry as an independent territory was through the award of the Nobel Prize to Ernst Otto Fischer and Geoffrey Wilkinson underlined. In 2005, Yves Chauvin, Robert H. Grubbs and Richard R. Schrock received the Nobel Prize for metal -catalyzed alkene metathesis.
A portion of the organometallic chemistry is the chemistry bioorganometallic examined which direct metal- carbon bonds in living organisms. Examples of such compounds are the methylcobalamin (vitamin B12) and adenosylcobalamin (coenzyme B12). Organometallic bond consisting of vitamin B12 from a direct cobalt -carbon bond: one cobalt atom, which sits in the center of a ring system ( corrin ring ), either linked to a methylene group, a cyanide ion, or with the 5'- carbon of deoxyadenosine. This B12 - substance group is thus probably the only vital, naturally occurring compound that has to be counted because of their direct metal -carbon bond to the metal- organic compounds in the narrower sense.
Classification of organometallic chemistry
Major classification schemes for the organometallic compounds are:
- For the metal, for example: Alkali metal organyls, such as butyllithium used for syntheses
- Erdalkalimetallorganyle such as magnesium organyls, such as the above-mentioned Grignard reagents
- Organyls the boron group, eg Organylaluminum as DIBAL or ones that are self-igniting and used in flamethrowers were
- Münzmetallorganyle, eg organic copper compounds, carboplatin
- For typical structural elements, for example: Sandwich complexes - they contain one metal atom or ion sandwiched between two aromatic rings. The bis-cyclopentadienyl iron or ferrocene is the most famous sandwich compound
- Carbene complexes - They are characterized by a metal -carbon double bond.
- According to the valency of the metal, particularly in the sub-group metals
Properties of organometallic compounds
Usually organylmetal are flammable. Sometimes they are even flammable ( pyrophoric ) and ignite spontaneously in air. Wherein the base metal organyls burns not only the organic residue, but also, the metal: it responds to the metal oxide. While, the metal atoms are embedded in a solid metal in a good heat-conducting environment, they are atomically dispersed in the metal- organic compounds, such that the reaction proceeds most intense as in a solid metal.
Many organylmetal, especially those of the alkali metals are very strong bases - some are among the strongest bases at all. They often react explosively with water and are unstable in weakly acidic environment.
Air - or moisture-sensitive organylmetal usually have to be stored and handled under inert gas or in an inert solvent ( Schlenk technique).
Affiliation of the subject area
According to the current definition of organic chemistry are compounds that contain carbon and hydrogen at the same time, organic, and accordingly, the organometallic compounds of organic chemistry would be counted. On the other hand, the chemistry of metals and metal ions has traditionally belonged to the field of inorganic chemistry. Therefore, some see a classification either "organic" or " inorganic " just here as a little purpose and consider the Organometallic Chemistry as an area in which large areas of overlap - or even as a separate subject area. On the other hand, it may be useful to moor the distinction on the basis of viewpoint. If the focus of research on the properties of the metal or element, it is Inorganic Chemistry. If the organometallic compound, however, used only as a means for modification of a purely organic molecule, so that counts for organic chemistry. Only when the carbon -metal bond as such is the focus of interest, it shall be said of pure metal-organic chemistry.
The classification of substances such as metal carbonyls (e.g., tetracarbonyl Ni ( CO) 4 ) containing bound to metal atoms of carbon monoxide, also shows the inadequacy too rigid classification schemes: carbon monoxide as carbon dioxide calculated traditionally one of the inorganic substances, which suggests that the metal carbonyls are inorganic. On the other hand, binds CO in the carbonyl complexes via its carbon atom to the metal, and the chemical properties of carbonyl complexes suggest that it would involve them in the Organometallic Chemistry.