Organometallic chemistry 22526 223410854 2008-07-03T23:26:47Z Endtothemeans 3893984 Added links [[Image:N-butyllithium-tetramer-3D-balls.png|thumb|right|200px|[[n-butyllithium|''n''-Butyllithium]], an organometallic compound.]] '''Organometallic chemistry''' is the study of [[chemical compound]]s containing [[chemical bonding|bonds]] between [[carbon]] and a [[metal]].<ref name="crabtree">{{cite book | title=The Organometallic Chemistry of the Transition Metals| url=http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471662569.html| author=[[Robert H. Crabtree]]| date=2005| pages=560| publisher=Wiley| id=ISBN 978-0-471-66256-3}}</ref><ref>{{cite web | title = Organometallics Defined | publisher = Interactive Learning Paradigms Incorporated | author = Toreki, R. | url = http://www.ilpi.com/organomet/organometallics.html | date = 2003-11-20}}</ref> 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-" e.g. organopalladium compounds. Examples of such organometallic compounds include all [[Gilman reagent|Gilman]] which contain [[lithium]] and [[copper]]. [[Tetracarbonyl nickel]], and [[ferrocene]] are examples of organometallic compounds containing [[transition metal]]s. Other examples include organomagnesium compounds like iodo(methyl)magnesium MeMgI, diethylmagnesium (Et<sub>2</sub>Mg), and all [[Grignard reagent]]s; organolithium compounds such as butyllithium (BuLi), organozinc compounds such as chloro(ethoxycarbonylmethyl)zinc (ClZnCH<sub>2</sub>C(=O)OEt); and organocopper compounds such as lithium dimethylcuprate (Li<sup>+</sup>[CuMe<sub>2</sub>]<sup>–</sup>). In addition to the traditional metals and semimetals, elements such as [[boron]], [[silicon]], [[arsenic]], and [[selenium]] are considered to form organometallic compounds, e.g. organoborane compounds such as triethylborane (Et<sub>3</sub>B). ===Coordination compounds with organic ligands=== Many [[Complex (chemistry)|complex]]es feature [[coordination bond]]s between a metal and organic ligands. The organic ligands often bind the metal through a heteroatom such as oxygen or nitrogen, in which case such compounds are considered coordination compounds. However, if any of the ligands form a direct M-C bond, then complex is usually considered to be organometallic, e.g., [(C<sub>6</sub>H<sub>6</sub>)Ru(H<sub>2</sub>O)<sub>3</sub>]<sup>2+</sup>. Furthermore, many lipophilic compounds such as metal [[acetylacetonate]]s and metal [[alkoxide]]s are called "metalorganics." Many organic coordination compounds occur naturally. For example, [[hemoglobin]] and [[myoglobin]] contain an [[iron]] center coordinated to the nitrogen atoms of a [[porphyrin]] ring; [[magnesium]] is the center of a [[chlorin]] ring in [[chlorophyll]]. The field of such [[inorganic compound]]s is known as [[bioinorganic chemistry]]. In contrast to these coordination compounds, [[methylcobalamin]] (a form of [[Vitamin B12|Vitamin B<sub>12</sub>]]), with a [[cobalt]]-[[methyl]] bond, is a true organometallic complex, one of the few known in biology. This subset of complexes are often discussed within the subfield of [[bioorganometallic chemistry]]. Illustrative of the many functions of the B<sub>12</sub>-dependent enzymes, the [[5-Methyltetrahydrofolate-homocysteine methyltransferase|MTR]] enzyme catalyzes the transfer of a methyl group from a nitrogen on [[N5-methyl-tetrahydrofolate]] to the sulfur of [[homocysteine]] to produce [[methionine]]. ===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 bond]]s, 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 are 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 orbital]]s of the organic moiety ligate the metal. ==Applications== Organometallics find practical uses as [[stoichiometric]] and [[catalyst|catalytically]] active compounds. [[Tetraethyl lead]] previously was combined with [[gasoline]] as an [[antiknock agent]]. Due to lead's toxicity it is 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. Similarly, the [[Wacker process]] is used in the oxidation of [[Olefins]]. 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 common industrial organometallic compound is the [[Grubbs catalyst]], a [[carbenoid]] (an organometallic compound of a [[carbene]] and a metal). Organometallic compounds of the reactive metals such as [[lithium]] or [[zinc]] are extremely basic and may also act as reductants. These [[superbase]]s are used in organic syntheses. [[Butyllithium]] is an example, widely used in synthetic organic chemistry. They are air-sensitive, however, and their flammability severely limits their industrial use. ==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 spectroscopy|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: * [[oxidative addition]] and [[reductive elimination]] * [[transmetalation]] * [[carbometalation]] * [[Hydrometalation]] * [[electron transfer]] * [[beta-hydride elimination]] * [[organometallic substitution reaction]] * [[carbon-hydrogen bond activation]] * [[cyclometalation]] == History == Early developments in organometallic chemistry include [[Louis Claude Cadet de Gassicourt|Louis Claude Cadet]]’s synthesis of methyl arsenic compounds related to [[cacodyl]], [[William Christopher Zeise]]'s [[Zeise's salt|platinum-ethylene complex]], [[Edward Frankland]]’s discovery of [[dimethyl zinc]], [[Ludwig Mond]]’s discovery of [[tetracarbonyl nickel|Ni(CO)<sub>4</sub>]], 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<sub>2</sub>, and alkenes as feedstocks and ligands. Recognition of organometallic chemistry as a distinct subfield culminated in the Nobel Prizes to [[Ernst Otto Fischer|Ernst Fischer]] and [[Geoffrey Wilkinson]] for work on [[metallocene]]s. 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 (chemist)|Paul Sabatier]] works on [[hydrogenation]] organic compounds with metal catalysts. Hydrogenation of [[fat]]s 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 (chemist)|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 compound]]s * 2005 [[Nobel prize]] [[Yves Chauvin]], [[Robert Grubbs]], and [[Richard Schrock]] on metal-catalyzed [[olefin metathesis|alkene metathesis]] == Organometallics == * [[Period 2 element]]s: [[organolithium chemistry]], [[organoberyllium chemistry]], [[organoborane chemistry]], * [[Period 3 element]]s: [[organomagnesium chemistry]], [[organoaluminum chemistry]], [[organosilicon chemistry]] * [[Period 4 element]]s: [[organotitanium chemistry]],[[organochromium chemistry]], [[organomanganese chemistry]] [[organoiron chemistry]], [[organocobalt chemistry]] [[organonickel chemistry]], [[organocopper chemistry]], [[organozinc chemistry]], [[organogallium chemistry]], [[organogermanium chemistry]] * [[Period 5 element]]s: [[organopalladium chemistry]], [[organosilver chemistry]], [[organocadmium chemistry]], [[organoindium chemistry]], [[organotin chemistry]] * [[Period 6 element]]s: [[organoplatinum chemistry]], [[organogold chemistry]], [[organomercury chemistry]],[[organothallium chemistry]], [[organolead chemistry]] == See also == *[[Chelation]] *[[Bioorganometallic chemistry]] == References == <div class="references-small"><references/></div> == External links == * [http://ocw.mit.edu/OcwWeb/Chemistry/5-44Fall-2004/CourseHome/index.htm MIT OpenCourseWare: Organometallic Chemistry] * [http://www.ilpi.com/organomet/ Rob Toreki's Organometallic HyperTextbook] {{Organometallics}} {{BranchesofChemistry}} [[Category:Organometallic chemistry|*]] [[bn:জৈব-ধাতব রসায়ন]] [[ca:Compost organometàl·lic]] [[cs:Organokovová chemie]] [[de:Organometallchemie]] [[es:Química organometálica]] [[fr:Composé organométallique]] [[ko:유기금속화학]] [[id:Kimia organologam]] [[it:Chimica metallorganica]] [[he:כימיה אורגנומתכתית]] [[la:Chemia Organometallica]] [[lb:Organometallchimie]] [[lt:Organometaliniai junginiai]] [[hu:Fémorganikus kémia]] [[mk:Органометално соединение]] [[nl:Organometaalchemie]] [[ja:有機金属化学]] [[pl:Związki metaloorganiczne]] [[pt:Composto organometálico]] [[ru:Металлоорганические соединения]] [[simple:Organometallic compound]] [[su:Kimia organologam]] [[th:ออร์แกนโนเมทัลลิกเคมี]] [[tr:Organometalik kimya]] [[uk:Металоорганічні сполуки]] [[zh:有机金属化学]]