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Transition Metal Alkene Complexes
In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. The inventory is large.Elschenbroich, C. "Organometallics" (2006) Wiley-VCH: Weinheim. Such compounds are intermediates in many catalytic reactions that convert alkenes to other organic products. Monoalkenes Complexes of ethylene are particularly common. Examples include Zeise's salt (see figure), Rh2Cl2(C2H4)4, Cp*2Ti(C2H4), and . Homoleptic alkene-complexes are well known but often are highly reactive. Examples include Ni(C2H4)3, o(C2H4)4sup>−, and e(C2H4)4sup>2−. Substituted monoalkenes are common ligands. Cyclooctene is found in chlorobis(cyclooctene)rhodium dimer. Alkenes with electron-withdrawing groups commonly bind strongly to low-valent metals. Examples of such ligands are TCNE, tetrafluoroethylene, maleic anhydride, and esters of fumaric acid. These acceptors form adducts with many zero-valent metals. Dienes, trienes, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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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 carbonyl, 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 "metalorganics, metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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(Benzylideneacetone)iron Tricarbonyl
(Benzylideneacetone)iron tricarbonyl is the organoiron compound with the formula (CHCH=CHC(O)CH)Fe(CO). It is a reagent for transferring the Fe(CO) unit. This red-colored compound is commonly abbreviated (bda)Fe(CO). Structure and bonding (bda)Fe(CO) is an example of a complex of an η-ketone. It is a piano stool complex. The compound is characterized by IR bands at 2065, 2005, and 1985 cm (cyclohexane solution), the three bands being indicative of the low symmetry of the complex, which is chiral. Synthesis, reactions, related reagents It is prepared by the reaction of Fe(CO) with benzylideneacetone. (bda)Fe(CO) sometimes reacts with Lewis bases to give adducts without displacement of the bda. The reagents of the type (bda)Fe(CO)(PR) function as sources of "Fe(CO)(PR)" (R = aryl, etc.). Other sources of Fe(CO) are Fe(CO) and Fe(CO)( cyclooctene). The latter is highly reactive and thermally sensitive. Imine derivatives of cinnamaldehyde, e.g. CHCH=CHC(H)=NCH, also for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Migratory Insertion
In organometallic chemistry, a migratory insertion is a type of chemical reaction, reaction wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the Reaction mechanism, mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing Chemical bond, bond of typically a second chemical entity e.g.: : + \longrightarrow Overview In the migratory insertion, a ligand that is viewed as an anion (X) ligand in and a ligand that is viewed as Neutral particle, neutral couple, generating a new anionic ligand. The anion and neutral ligands that react are adjacent. If the Precursor (chemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Cyclopentadienyl
Cyclopentadienyl can refer to * Cyclopentadienyl anion, or cyclopentadienide, ** Cyclopentadienyl ligand * Cyclopentadienyl radical, • * Cyclopentadienyl cation, See also * Pentadienyl {{Chemistry index ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Lewis Base
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH3 is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane CH3)3Bis a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. In the context of a specific chemical reaction between NH3 and Me3B, a lone pair from NH3 will form a dative bond with the empty orbital of Me3B to form an adduct NH3•BMe3. The terminology refers to the contributions of Gilbert N. Lewis. From p. 142: "We are inclined to think of substances as pos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Lewis Acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH3 is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane CH3)3Bis a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. In the context of a specific chemical reaction between NH3 and Me3B, a lone pair from NH3 will form a dative bond with the empty orbital of Me3B to form an adduct NH3•BMe3. The terminology refers to the contributions of Gilbert N. Lewis. From p. 142: "We are inclined to think of substances as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Dewar–Chatt–Duncanson Model
The Dewar–Chatt–Duncanson model is a model in organometallic chemistry that explains the chemical bonding in transition metal alkene complexes. The model is named after Michael J. S. Dewar, Joseph Chatt and L. A. Duncanson. The alkene donates electron density into a π-acid metal d-orbital from a σ-symmetry bonding orbital between the carbon atoms. The metal donates electrons back from a (different) filled d-orbital into the empty π* antibonding orbital. Both of these effects tend to reduce the carbon-carbon bond order, leading to an elongated C−C distance and a lowering of its vibrational frequency. In Zeise's salt K PtCl3(C2H4)">platinum.html" ;"title="/nowiki>platinum">PtCl3(C2H4)sup>.H2O the C−C bond length has increased to 134 picometres from 133 pm for ethylene. In the nickel compound Ni(C2H4)(PPh3)2 the value is 143 pm. The interaction also causes carbon atoms to "rehybridise" from sp2 towards sp3, which is indicated by the bending of the hydrogen atoms o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Xylylene
In organic chemistry, a xylylene (sometimes quinone-dimethide) is any of the constitutional isomers having the formula C6H4(CH2)2. These compounds are related to the corresponding quinones and quinone methides by replacement of the oxygen atoms by CH2 groups. Arene substitution patterns, ''ortho''- and ''para''-xylylene are best known, although neither is stable in solid or liquid form. The ''meta'' form is a diradical. Certain substituted derivatives of xylylenes are however highly stable, such as tetracyanoquinodimethane and the xylylene dichlorides. p-Xylylene ''p''-Xylylene forms upon pyrolysis of ''p''-xylene or, more readily, the α-substituted derivatives. ''p''-Xylylene Dimer (chemistry), dimerizes with moderate efficiency to give ''p''-cyclophane: Further heating of the ''p''-cyclophane gives Parylene, poly(''para''-xylylene). o-Xylylenes o-Xylylenes (''o''-quinodimethanes) are often generated in situ, e.g., by the pyrolysis of the corresponding sulfone. Another met ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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(Norbornadiene)molybdenum Tetracarbonyl
(Norbornadiene)molybdenum tetracarbonyl is the organomolybdenum compound with the formula (C7H9)Mo(CO)4. Structurally, the compound consists of the norbornadiene bonded to a Mo(CO)4 fragment. The compound is a yellow, volatile solid. It is prepared by thermal or photochemical substitution of molybdenum hexacarbonyl. The compound was originally examined as a potential antiknock agent An antiknock agent (also: knock inhibitor) is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, .... (Norbornadiene)molybdenum tetracarbonyl is a precursor to other derivatives of the type L2Mo(CO)4. This conversion exploits the lability of the diene ligand: :(C7H9)Mo(CO)4 + 2 L → C7H9 + L2Mo(CO)4 References External links * {{DEFAULTSORT:Norbornadiene)molybdenum tetracarbonyl Molybdenum(0) compounds Carbonyl complexes Octahedral comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Fe(COT)2
Bis(cyclooctatetraene)iron is an organoiron compound with the formula Fe(C8H8)2, abbreviated Fe(COT)2. It is an air-sensitive black solid that is soluble in diethyl ether and aromatic solvents. The compound decomposes in solution after a few days even under inert atmosphere. It has no known practical applications but has been studied as a soluble source of Fe(0). Preparation The laboratory synthesis of Fe(COT)2, using Schlenk techniques, involves reduction of ferric acetylacetonate by triethylaluminium in the presence of 1,3,5,7-cyclooctatetraene: :Fe(C5H7O2)3 + 2 C8H8 + 3 Al(C2H5)3 → Fe(C8H8)2 + 3 Al(C2H5)2(C5H7O2) + C2H4 + C2H6 Structure According to analysis by single crystal X-ray crystallography, the two cyclooctatetraene rings bind differently to the Fe center, leading to the description Fe(''η''4-C8H8)(''η''6-C8H8). One cyclooctatetraene ring binds to Fe with two adjacent double bonds. This interaction is similar to that in (''η''4-C8H8)Fe( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Crabtree's Catalyst
Crabtree's catalyst is an organoiridium compound with the formula C5H5N">Tricyclohexylphosphine">P(C6H11)3pyridine">C5H5N/nowiki>PF6. It is a homogeneous catalyst for hydrogenation and hydrogen-transfer reactions, developed by Robert H. Crabtree. This air stable orange solid is commercially available and known for its directed hydrogenation to give trans stereoselectivity with respective of directing group. Structure and synthesis The cation has a square planar molecular geometry, as expected for a d8 complex. It is prepared from cyclooctadiene iridium chloride dimer. Reactivity Crabtree’s catalyst is effective for the hydrogenations of mono-, di-, tri-, and tetra-substituted substrates. Whereas Wilkinson’s catalyst and the Schrock–Osborn catalyst do not catalyze the hydrogenation of a tetrasubstituted olefin, Crabtree’s catalyst does so to at high turnover frequencies (table). : The catalyst is reactive at room temperature. The reaction is robust without drying sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |