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Bulky Cyclopentadienyl Ligands
In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is jargon for a ligand of the type where R is a branched alkyl and ''n'' = 3 or 4. Representative examples are the tetraisopropyl derivative and the tris( ''tert''-butyl) derivative . These ligands are so large that their complexes behave differently from the pentamethylcyclopentadienyl analogues. Because they cannot closely approach the metal, these bulky ligands stabilize high spin complexes, such as (C5H2''t''Bu3)2Fe2I2. These large ligands stabilize highly unsaturated derivatives such as (C5H2''t''Bu3)2Fe2N2. Synthesis and reactions The (''tert''-butyl)cyclopentadiene is prepared by alkylation of cyclopentadiene with ''tert''-butyl bromide in the presence of sodium hydride and dibenzo-18-crown-6. The intermediate in this synthesis is di-''tert''-butylcyclopentadiene. This compound is conveniently prepared by alkylation of cyclobutadiene with tert-butyl bromide under phase-transfer condi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopentadiene
Cyclopentadiene is an organic compound with the chemical formula, formula C5H6.LeRoy H. Scharpen and Victor W. Laurie (1965): "Structure of cyclopentadiene". ''The Journal of Chemical Physics'', volume 43, issue 8, pages 2765-2766. It is often abbreviated CpH because the cyclopentadienyl anion is abbreviated Cp−. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimer (chemistry), dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction. This dimer can be retro-Diels–Alder reaction, restored by heating to give the monomer. The compound is mainly used for the production of cyclopentene and its derivatives. It is popularly used as a precursor to the cyclopentadienyl anion (Cp−), an important ligand in cyclopentadienyl complexes in organometallic chemistry. Production and reactions Cyclopentadiene production is usually not distinguished from dicyclopentadiene since they interconvert. They ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cp*2Ir2Cl4
Pentamethylcyclopentadienyl iridium dichloride dimer is an organometallic compound with the formula C5(CH3)5IrCl2)sub>2, commonly abbreviated p*IrCl2sub>2 This bright orange air-stable diamagnetic solid is a reagent in organometallic chemistry. Structure The compound has C2h symmetry. Each metal is pseudo-octahedral. The terminal and bridging Ir-Cl bonds have the lengths 2.39 and 2.45 Å, respectively. Preparation, reactions Pentamethylcyclopentadienyl iridium dichloride dimer was first prepared by the reaction of hydrated iridium trichloride with hexamethyl Dewar benzene. More conveniently, the compound is prepared by the reaction of hydrated iridium trichloride and pentamethylcyclopentadiene in hot methanol, from which the product precipitates :2 Cp*H + 2 IrCl3(H2O)3 → p*IrCl2sub>2 + 2 HCl + 6 H2O The Ir-'' μ''-Cl bonds are labile and can be cleaved to give a variety of adducts of the general formula Cp*IrCl2L. Such adducts undergo further substitution to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrido Complex
Metal nitrido complexes are coordination compounds and metal clusters that contain an atom of nitrogen bound only to transition metals. These compounds are ''molecular'', i.e. discrete in contrast to the polymeric, dense nitride materials that are useful in materials science. The distinction between the molecular and solid-state polymers is not always very clear as illustrated by the materials Li6MoN4 and more condensed derivatives such as Na3MoN3. Transition metal nitrido complexes have attracted interest in part because it is assumed that nitrogen fixation proceeds via nitrido intermediates. Nitrido complexes have long been known, the first example being salts of sO3Nsup>−, described in the 19th century. Structural trends Mononuclear complexes feature terminal nitride ligands, typically with short M-N distances consistent with metal ligand multiple bonds. For example, in the anion in PPh4 oNCl4 the Mo-N distance is 163.7 pm. The occurrence of terminal nitrido ligands ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Di-tert-butylcyclopentadiene
Di-''tert''-butylcyclopentadiene is an organic compound with the formula (Me3C)2C5H4, where Me = methyl. It is a colorless liquid that is soluble in organic solvents. The compound is the conjugate acid of the di-''tert''-butylcyclopentadienyl ligand, (Me3C)2C5H3− (sometimes abbreviated Cp‡−). Two regioisomers of di-''tert''-butylcyclopentadiene exist, depending on the relative location of the double bonds In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw .... Synthesis and reactions Di-''tert''-butylcyclopentadiene is prepared by alkylation of cyclopentadiene with ''tert''-butyl bromide under phase-transfer conditions. It is the precursor to many metal complexes, such as the olefin polymerization catalyst ((Me3C)2C5H3)TiCl3.{{cite journal, doi=10.1021/OM980106R, title=Synt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dibenzo-18-crown-6
Dibenzo-18-crown-6 is the organic compound with the formula C6H4OCH2CH2OCH2CH2sub>2. It is a white solid that is soluble in organic solvents. As one of the most popular crown ethers, it facilitates the dissolution of many salts in organic solvents. It is related to the non-benzannulated 18-crown-6. Dibenzo-18-crown-6 can be synthesized from catechol Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ... and bis(chloroethyl) ether. : In contrast to those of 18-crown-6, complexes of the dibenzo crown are flattened, which often allows higher coordination numbers at the encapsulated metal cation. References Crown ethers Cyclophanes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Hydride
Sodium hydride is the chemical compound with the empirical formula Na H. This alkali metal hydride is primarily used as a strong yet combustible base in organic synthesis. NaH is a saline (salt-like) hydride, composed of Na+ and H− ions, in contrast to molecular hydrides such as borane, methane, ammonia, and water. It is an ionic material that is insoluble in organic solvents (although soluble in molten Na), consistent with the fact that H− ions do not exist in solution. Because of the insolubility of NaH, all reactions involving NaH occur at the surface of the solid. Basic properties and structure NaH is produced by the direct reaction of hydrogen and liquid sodium.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. . Pure NaH is colorless, although samples generally appear grey. NaH is ca. 40% denser than Na (0.968 g/cm3). NaH, like LiH, KH, RbH, and CsH, adopts the NaCl crystal structure. In this motif, each Na+ ion is surrounded by six H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 repres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Spin Complex
Crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually ''d'' or ''f'' orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). This theory has been used to describe various spectroscopies of transition metal coordination complexes, in particular optical spectra (colors). CFT successfully accounts for some magnetic properties, colors, hydration enthalpies, and spinel structures of transition metal complexes, but it does not attempt to describe bonding. CFT was developed by physicists Hans Bethe and John Hasbrouck van Vleck in the 1930s. CFT was subsequently combined with molecular orbital theory to form the more realistic and complex ligand field theory (LFT), which delivers insight into the process of chemical bonding in transition metal complexes. Overview of crystal field theory According to crystal field theory, the interaction between a transition metal and ligands arises from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentamethylcyclopentadienyl
1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic diene with the formula C5Me5H (Me = CH3). 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted Cp* (C5Me5) and read as "C P star", the "star" signifying the five methyl groups radiating from the core of the ligand. In contrast to less-substituted cyclopentadiene derivatives, Cp*H is not prone to dimerization. Synthesis Pentamethylcyclopentadiene is commercially available. It was first prepared from tiglaldehyde via 2,3,4,5-tetramethylcyclopent-2-enone. Alternatively, 2-butenyllithium adds to ethyl acetate followed by acid-catalyzed dehydrocyclization: Organometallic derivatives Cp*H is a precursor to organometallic compounds containing the ligand, commonly called Cp*−. Some representative reactions leading to such Cp*–metal complexes follow: :Cp*H + C4H9Li → Cp*Li + C4H10 :Cp*Li + TiCl4 → Cp*TiCl3 + LiCl Some Cp* co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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