In chemistry, homogeneous catalysis is catalysis where the catalyst is in same phase as reactants, principally by a soluble catalyst in a solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid and gas, respectively. The term is used almost exclusively to describe solutions and implies catalysis by organometallic compounds . Homogeneous catalysis is an established technology that continues to evolve. An illustrative major application is the production of acetic acid . Enzymes are examples of homogeneous catalysts.
28-664: HMDS may refer to: either of two related reagents in organometallic chemistry : Hexamethyldisilazane ([(CH 3 ) 3 Si] 2 NH) Hexamethyldisilazide ([(CH 3 ) 3 Si] 2 NM) M = Li as in Lithium bis(trimethylsilyl)amide (LiHMDS) M = Na as in Sodium bis(trimethylsilyl)amide (NaHMDS) M = K as in Potassium bis(trimethylsilyl)amide (KHMDS) Hexamethyldisiloxane (O[Si(CH 3 ) 3 ] 2 ) Her Majesty's Diplomatic Service , of
56-961: 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 . Subspecialty areas of organometallic chemistry include: Organometallic compounds find wide use in commercial reactions, both as homogenous catalysts and as stoichiometric reagents . For instance, organolithium , organomagnesium , and organoaluminium compounds , examples of which are highly basic and highly reducing, are useful stoichiometrically but also catalyze many polymerization reactions. Almost all processes involving carbon monoxide rely on catalysts, notable examples being described as carbonylations . The production of acetic acid from methanol and carbon monoxide
84-684: A heated substrate via metalorganic vapor phase epitaxy (MOVPE) process in the production of light-emitting diodes (LEDs). Organometallic compounds undergo several important reactions: The synthesis of many organic molecules are facilitated by organometallic complexes. Sigma-bond metathesis is a synthetic method for forming new carbon-carbon sigma bonds . Sigma-bond metathesis is typically used with early transition-metal complexes that are in their highest oxidation state. Using transition-metals that are in their highest oxidation state prevents other reactions from occurring, such as oxidative addition . In addition to sigma-bond metathesis, olefin metathesis
112-435: A mixed-valence iron-cyanide complex, was first prepared in 1706 by paint maker Johann Jacob Diesbach as the first coordination polymer and synthetic material containing a metal-carbon bond. ) 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
140-822: A prominent form of carbonylation , involves the addition of H and "C(O)H" across a double bond. This process is almost exclusively conducted with soluble rhodium - and cobalt -containing complexes. A related carbonylation is the conversion of alcohols to carboxylic acids. MeOH and CO react in the presence of homogeneous catalysts to give acetic acid , as practiced in the Monsanto process and Cativa processes . Related reactions include hydrocarboxylation and hydroesterifications . A number of polyolefins, e.g. polyethylene and polypropylene, are produced from ethylene and propylene by Ziegler-Natta catalysis . Heterogeneous catalysts dominate, but many soluble catalysts are employed especially for stereospecific polymers. Olefin metathesis
168-513: Is methylcobalamin (a form of Vitamin B 12 ), which contains a cobalt - methyl bond. This complex, along with other biologically relevant complexes are often discussed within the subfield of bioorganometallic chemistry . Many complexes feature coordination bonds between a metal and organic ligands . Complexes where the organic ligands bind the metal through a heteroatom such as oxygen or nitrogen are considered coordination compounds (e.g., heme A and Fe(acac) 3 ). However, if any of
196-400: Is a controversial animal feed additive. In 2006, approximately one million kilograms of it were produced in the U.S alone. Organotin compounds were once widely used in anti-fouling paints but have since been banned due to environmental concerns. Homogeneous catalysis The proton is a pervasive homogeneous catalyst because water is the most common solvent. Water forms protons by
224-881: Is catalyzed via metal carbonyl complexes in the Monsanto process and Cativa process . Most synthetic aldehydes are produced via hydroformylation . The bulk of the synthetic alcohols, at least those larger than ethanol, are produced by hydrogenation of hydroformylation-derived aldehydes. Similarly, the Wacker process is used in the oxidation of ethylene to acetaldehyde . Almost all industrial processes involving alkene -derived polymers rely on organometallic catalysts. The world's polyethylene and polypropylene are produced via both heterogeneously via Ziegler–Natta catalysis and homogeneously, e.g., via constrained geometry catalysts . Most processes involving hydrogen rely on metal-based catalysts. Whereas bulk hydrogenations (e.g., margarine production) rely on heterogeneous catalysts, for
252-1438: Is different from Wikidata All article disambiguation pages All disambiguation pages Organometallic chemistry Organometallic chemistry is the study of organometallic compounds , chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal , including alkali , alkaline earth , and transition metals , and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide ( metal carbonyls ), cyanide , or carbide , are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term " metalorganic compound " refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides , dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry . Organometallic compounds are widely used both stoichiometrically in research and industrial chemical reactions, as well as in
280-749: Is generally highly covalent . For highly electropositive elements, such as lithium and sodium, the carbon ligand exhibits carbanionic character, but free carbon-based anions are extremely rare, an example being cyanide . Most organometallic compounds are solids at room temperature, however some are liquids such as methylcyclopentadienyl manganese tricarbonyl , or even volatile liquids such as nickel tetracarbonyl . Many organometallic compounds are air sensitive (reactive towards oxygen and moisture), and thus they must be handled under an inert atmosphere . Some organometallic compounds such as triethylaluminium are pyrophoric and will ignite on contact with air. As in other areas of chemistry, electron counting
308-583: Is shared between ( delocalized ) a carbon atom and an atom more electronegative than carbon (e.g. 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. For instance, lithium enolates often contain only Li-O bonds and are not organometallic, while zinc enolates ( Reformatsky reagents ) contain both Zn-O and Zn-C bonds, and are organometallic in nature. The metal-carbon bond in organometallic compounds
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#1732845096836336-1150: Is used to synthesize various carbon-carbon pi bonds . Neither sigma-bond metathesis or olefin metathesis change the oxidation state of the metal. Many other methods are used to form new carbon-carbon bonds, including beta-hydride elimination and insertion reactions . Organometallic complexes are commonly used in catalysis. Major industrial processes include hydrogenation , hydrosilylation , hydrocyanation , olefin metathesis , alkene polymerization , alkene oligomerization , hydrocarboxylation , methanol carbonylation , and hydroformylation . Organometallic intermediates are also invoked in many heterogeneous catalysis processes, analogous to those listed above. Additionally, organometallic intermediates are assumed for Fischer–Tropsch process . Organometallic complexes are commonly used in small-scale fine chemical synthesis as well, especially in cross-coupling reactions that form carbon-carbon bonds, e.g. Suzuki-Miyaura coupling , Buchwald-Hartwig amination for producing aryl amines from aryl halides, and Sonogashira coupling , etc. Natural and contaminant organometallic compounds are found in
364-454: Is useful for organizing organometallic chemistry. The 18-electron rule is helpful in predicting the stabilities of organometallic complexes, for example metal carbonyls and metal hydrides . The 18e rule has two representative electron counting models, ionic and neutral (also known as covalent) ligand models, respectively. The hapticity of a metal-ligand complex, can influence the electron count. Hapticity (η, lowercase Greek eta), describes
392-471: Is usually catalyzed heterogeneously in industry, but homogeneous variants are valuable in fine chemical synthesis. Homogeneous catalysts are also used in a variety of oxidations. In the Wacker process , acetaldehyde is produced from ethene and oxygen . Many non-organometallic complexes are also widely used in catalysis, e.g. for the production of terephthalic acid from xylene . Alkenes are epoxidized and dihydroxylated by metal complexes, as illustrated by
420-509: The Halcon process and the Sharpless dihydroxylation . Enzymes are homogeneous catalysts that are essential for life but are also harnessed for industrial processes. A well-studied example is carbonic anhydrase , which catalyzes the release of CO 2 into the lungs from the bloodstream. Enzymes possess properties of both homogeneous and heterogeneous catalysts. As such, they are usually regarded as
448-476: The isolobal principle . A wide variety of physical techniques are used to determine the structure, composition, and properties of organometallic compounds. X-ray diffraction is a particularly important technique that can locate the positions of atoms within a solid compound, providing a detailed description of its structure. Other techniques like infrared spectroscopy and nuclear magnetic resonance spectroscopy are also frequently used to obtain information on
476-616: The United Kingdom Helmet mounted display and sight , a system for military pilots Harvest Moon DS , a video game Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title HMDS . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=HMDS&oldid=856936070 " Category : Disambiguation pages Hidden categories: Short description
504-416: The electron donating interactions of the ligand. Many organometallic compounds do not follow the 18e rule. The metal atoms in organometallic compounds are frequently described by their d electron count and oxidation state . These concepts can be used to help predict their reactivity and preferred geometry . Chemical bonding and reactivity in organometallic compounds is often discussed from the perspective of
532-412: The environment. Some that are remnants of human use, such as organolead and organomercury compounds, are toxicity hazards. Tetraethyllead was prepared for use as a gasoline additive but has fallen into disuse because of lead's toxicity. Its replacements are other organometallic compounds, such as ferrocene and methylcyclopentadienyl manganese tricarbonyl (MMT). The organoarsenic compound roxarsone
560-448: The ligands form a direct metal-carbon (M-C) bond, then the complex is considered to be organometallic. Although the IUPAC has not formally defined the term, some chemists use the term "metalorganic" to describe any coordination compound containing an organic ligand regardless of the presence of a direct M-C bond. The status of compounds in which the canonical anion has a negative charge that
588-562: The number of contiguous ligands coordinated to a metal. For example, ferrocene , [(η -C 5 H 5 ) 2 Fe], has two cyclopentadienyl ligands giving a hapticity of 5, where all five carbon atoms of the C 5 H 5 ligand bond equally and contribute one electron to the iron center. Ligands that bind non-contiguous atoms are denoted the Greek letter kappa, κ. Chelating κ2-acetate is an example. The covalent bond classification method identifies three classes of ligands, X,L, and Z; which are based on
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#1732845096836616-828: The process of self-ionization of water . In an illustrative case, acids accelerate (catalyze) the hydrolysis of esters : At neutral pH, aqueous solutions of most esters do not hydrolyze at practical rates. A prominent class of reductive transformations are hydrogenations . In this process, H 2 added to unsaturated substrates. A related methodology, transfer hydrogenation , involves by transfer of hydrogen from one substrate (the hydrogen donor) to another (the hydrogen acceptor). Related reactions entail "HX additions" where X = silyl ( hydrosilylation ) and CN ( hydrocyanation ). Most large-scale industrial hydrogenations – margarine, ammonia, benzene-to-cyclohexane – are conducted with heterogeneous catalysts. Fine chemical syntheses, however, often rely on homogeneous catalysts. Hydroformylation ,
644-469: The production of fine chemicals such hydrogenations rely on soluble (homogenous) organometallic complexes or involve organometallic intermediates. Organometallic complexes allow these hydrogenations to be effected asymmetrically. Many semiconductors are produced from trimethylgallium , trimethylindium , trimethylaluminium , and trimethylantimony . These volatile compounds are decomposed along with ammonia , arsine , phosphine and related hydrides on
672-594: The result of hydroboration and carboboration reactions. Tetracarbonyl nickel and ferrocene are examples of organometallic compounds containing transition metals . Other examples of organometallic compounds include organolithium compounds such as n -butyllithium (n-BuLi), organozinc compounds such as diethylzinc (Et 2 Zn), organotin compounds such as tributyltin hydride (Bu 3 SnH), organoborane compounds such as triethylborane (Et 3 B), and organoaluminium compounds such as trimethylaluminium (Me 3 Al). A naturally occurring organometallic complex
700-439: The role of catalysts to increase the rates of such reactions (e.g., as in uses of homogeneous catalysis ), where target molecules include polymers, pharmaceuticals, and many other types of practical products. Organometallic compounds are distinguished by the prefix "organo-" (e.g., organopalladium compounds), and include all compounds which contain a bond between a metal atom and a carbon atom of an organyl group . In addition to
728-738: The structure and bonding of organometallic compounds. Ultraviolet-visible spectroscopy is a common technique used to obtain information on the electronic structure of organometallic compounds. It is also used monitor the progress of organometallic reactions, as well as determine their kinetics . The dynamics of organometallic compounds can be studied using dynamic NMR spectroscopy . Other notable techniques include X-ray absorption spectroscopy , electron paramagnetic resonance spectroscopy , and elemental analysis . Due to their high reactivity towards oxygen and moisture, organometallic compounds often must be handled using air-free techniques . Air-free handling of organometallic compounds typically requires
756-474: The traditional metals ( alkali metals , alkali earth metals , transition metals , and post transition metals ), lanthanides , actinides , semimetals, and the elements boron , silicon , arsenic , and selenium are considered to form organometallic compounds. Examples of organometallic compounds include Gilman reagents , which contain lithium and copper , and Grignard reagents , which contain magnesium . Boron-containing organometallic compounds are often
784-519: The use of laboratory apparatuses such as a glovebox or Schlenk line . 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 diethyl- and dimethylzinc , Ludwig Mond 's discovery of Ni(CO) 4 , and Victor Grignard 's organomagnesium compounds. (Although not always acknowledged as an organometallic compound, Prussian blue ,
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