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Biferrocene
Biferrocene is the organometallic compound with the formula C5H5)Fe(C5H4)sub>2. It is the product of the formal dehydrocoupling of ferrocene, analogous the relationship between biphenyl and benzene. It is an orange, air-stable solid that is soluble in nonpolar organic solvents. Biferrocene can be prepared by the Ullmann coupling of iodoferrocene. Its one-electron oxidized derivative C5H5)Fe(C5H4)sub>2+ attracted attention as a prototypical mixed-valence compound. A related compound is biferrocenylene, e(C5H4)2sub>2 wherein all cyclopentadienyl rings are coupled. Formally, biferrocene is derived from one fulvalene ligand, and biferrocenylene is derived from two. Reactions Biferrocene can easily be converted into a mixed-valence complex, which is called biferrocenium. This e(II)-Fe(III)cation is a class II type (0.707 > α > 0) mixed-valence complex according to the Robin-Day classification. Derivatives Aminophosphine ligands with biferroceno substitutents have been p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fulvalene
Fulvalene (bicyclopentadienylidene) is the member of the fulvalene family with the molecular formula C10H8. It is of theoretical interest as one of the simplest non-benzenoid conjugated hydrocarbons. Fulvalene is an unstable isomer of the more common benzenoid aromatic compounds naphthalene and azulene. Fulvalene consists of two 5-membered rings, each with two double bonds, joined by yet a fifth double bond. It has D2h symmetry. History An earlier attempt at synthesis of fulvalene in 1951 by Pauson and Kealy resulted in the accidental discovery of ferrocene. Its synthesis was first reported in 1958 by E. A. Matzner, working under William von Eggers Doering. In this method, cyclopentadienyl anion is coupled with iodine to the dihydrofulvalene. Double deprotonation of dihydrofulvalene with ''n''-butyllithium gives the dilithio derivative, which oxidizes with oxygen. Fulvalene was spectroscopically observed at from photolysis of diazocyclopentadiene, which induces dimer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferrocene
Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, and is soluble in most organic solvents. It is remarkable for its stability: it is unaffected by air, water, strong bases, and can be heated to 400 °C without decomposition. In oxidizing conditions it can reversibly react with strong acids to form the ferrocenium cation . The rapid growth of organometallic chemistry is often attributed to the excitement arising from the discovery of ferrocene and its many analogues, such as metallocenes. History Discovery Ferrocene was discovered by accident thrice. The first known synthesis may have been made in the late 1940s by unknown researchers at Union Carbide, who tried to pass hot cyclopentadiene vapor through an iron pipe. The vapor reacted with the pipe wall, creating a "yellow sludg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bis(fulvalene)diiron
Bis(fulvalene)diiron is the organoiron complex with the formula (C5H4-C5H4)2Fe2. Structurally, the molecule consists of two ferrous centers sandwiched between fulvalene dianions. The compound is an orange solid with lower solubility in benzene than ferrocene. Its structure has been verified by X-ray crystallography. The compound has attracted some interest for its redox properties. Preparation It was first prepared by Ullmann coupling of 1,1'-diiodoferrocene using copper but subsequent work produces the complex is 20-40% yield from dilithiofulvalene and ferrous chloride: :2(C5H4Li)2 + 2FeCl2 → (C5H4-C5H4)2Fe2 + 4{{nbspLiCl Related compounds * Biferrocene Biferrocene is the organometallic compound with the formula C5H5)Fe(C5H4)sub>2. It is the product of the formal dehydrocoupling of ferrocene, analogous the relationship between biphenyl and benzene. It is an orange, air-stable solid that is solu ... References Ferrocenes Sandwich compounds Cyclopentadienyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organometallic Compound
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 "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 phosphine complex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ullmann Coupling
The Ullmann reaction or Ullmann coupling is a coupling reaction between aryl halides. Traditionally this reaction is effected by copper, but palladium and nickel are also effective catalysts. The reaction is named after Fritz Ullmann. Mechanism The mechanism of the Ullmann reaction is extensively studied. Complications arise because the reactions are often heterogeneous. With copper as the halide acceptor, organocopper intermediates are invoked. Scope A typical example of classic Ullmann biaryl coupling is the conversion of ''ortho''-chloronitrobenzene into 2,2'-dinitrobiphenyl with a copper - bronze alloy. : : The traditional version of the Ullmann reaction requires harsh reaction conditions, and the reaction has a reputation for erratic yields. Because of these problems many improvements and alternative procedures have been introduced. The classical Ullmann reaction is limited to electron deficient aryl halides and requires harsh reaction conditions. Modern variants of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixed-valence
Inner sphere electron transfer (IS ET) or bonded electron transfer is a redox chemical reaction that proceeds via a covalent linkage—a strong electronic interaction—between the oxidant and the reductant reactants. In inner sphere electron transfer, a ligand bridges the two metal redox centers during the electron transfer event. Inner sphere reactions are inhibited by large ligands, which prevent the formation of the crucial bridged intermediate. Thus, inner sphere ET is rare in biological systems, where redox sites are often shielded by bulky proteins. Inner sphere ET is usually used to describe reactions involving transition metal complexes and most of this article is written from this perspective. However, redox centers can consist of organic groups rather than metal centers. The bridging ligand could be virtually any entity that can convey electrons. Typically, such a ligand has more than one lone electron pair, such that it can serve as an electron donor to both the red ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopentadienyl
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Cyclopentadienyl can refer to *Cyclopentadienyl anion, or cyclopentadienide, **Cyclopentadienyl ligand *Cyclopentadienyl radical, • *Cyclopentadienyl cation, See also *Pentadienyl In organic chemistry, pentadienyl refers to the organic radical, anion, or cation with the formula , where ''z'' = 0, −1, +1, respectively. Organometallic chemistry In organometallic chemistry, the pentadienyl anion is a ligand, the acyclic ana ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixed-valence Complex
Mixed valence complexes contain an element which is present in more than one oxidation state. Well-known mixed valence compounds include the Creutz–Taube complex, Prussian blue, and molybdenum blue. Many solids are mixed-valency including indium chalcogenides. Robin–Day classification Mixed-valence compounds are subdivided into three groups, according to the Robin–Day classification: *Class I, where the valences are trapped—localized on a single site—such as Pb3O4 and antimony tetroxide. There are distinct sites with different specific valences in the complex that cannot easily interconvert. *Class II, which are intermediate in character. There is some localization of distinct valences, but there is a low activation energy for their interconversion. Some thermal activation is required to induce electron transfer from one site to another via the bridge. These species exhibit an intense Intervalence charge transfer (IT or IVCT) band, a broad intense absorption in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aminophosphine
In organophosphorus chemistry, an aminophosphine is a compound with the formula R3−nP(NR2)n where R = H or an organic substituent, and n = 0, 1, 2. At one extreme, the parent H2PNH2 is lightly studied and fragile, but at the other extreme tris(dimethylamino)phosphine (P(NMe2)3) is commonly available. Intermediate members are known, such as Ph2PN(H)Ph. These compounds are typically colorless and reactive toward oxygen. They have pyramidal geometry at phosphorus. Parent members The fundamental aminophosphines have the formulae PH2−n(NH2)n (n = 1, 2, 3). These species cannot be isolated in a practical quantities, although they have been examined theoretically. H2NPH2 is predicted to be more stable than the P(V) tautomer HN=PH3. With secondary amines, the chemistry is more straightforward. Trisaminophosphines are prepared by treatment of phosphorus trichloride with secondary amines: :PCl3 + 6 HNMe2 → (Me2N)3P + 3 [H2NMe2]Cl Aminophosphine chlorides The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allylic Rearrangement
An allylic rearrangement or allylic shift is an organic reaction in which the double bond in an allyl chemical compound shifts to the next carbon atom. It is encountered in nucleophilic substitution. In reaction conditions that favor a SN1 reaction mechanism, the intermediate is a carbocation for which several resonance structures are possible. This explains the product distribution (or product spread) after recombination with nucleophile Y. This type of process is called an SN1' substitution. Alternatively, it is possible for nucleophile to attack directly at the allylic position, displacing the leaving group in a single step, in a process referred to as SN2' substitution. This is likely in cases when the allyl compound is unhindered, and a strong nucleophile is used. The products will be similar to those seen with SN1' substitution. Thus reaction of 1-chloro-2-butene with sodium hydroxide gives a mixture of 2-buten-1-ol and 3-buten-2-ol: : Nevertheless, the product in whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymmetric Hydrogenation
Asymmetric hydrogenation is a chemical reaction that adds two atoms of Hydrogen atom, hydrogen to a target (substrate) molecule with three-dimensional Enantioselective synthesis, spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information (what chemists refer to as chirality) to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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