|
Cyclooctadiene Iridium Chloride Dimer
Cyclooctadiene iridium chloride dimer is an organoiridium compound with the formula r(μ2-Cl)(COD)sub>2, where COD is the diene 1,5-cyclooctadiene (C8H12). It is an orange-red solid that is soluble in organic solvents. The complex is used as a precursor to other iridium complexes, some of which are used in homogeneous catalysis. The solid is air-stable but its solutions degrade in air. Preparation, structure, reactions The compound is prepared by heating hydrated iridium trichloride and cyclooctadiene in alcohol solvent. In the process, Ir(III) is reduced to Ir(I). In terms of its molecular structure, the iridium centers are square planar as is typical for a d8 complex. The Ir2Cl2 core is folded with a dihedral angle of 86°. The molecule crystallizes in yellow-orange and red-orange polymorphs; the latter one is more common. The complex is widely used precursor to other iridium complexes. A notable derivative is Crabtree's catalyst. The chloride ligands can also be repla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoiridium Compound
Organoiridium chemistry is the chemistry of organometallic compounds containing an iridium-carbon chemical bond. Organoiridium compounds are relevant to many important processes including olefin hydrogenation and the industrial synthesis of acetic acid. They are also of great academic interest because of the diversity of the reactions and their relevance to the synthesis of fine chemicals. Classification based on principal oxidation states Organoiridium compounds share many characteristics with those of rhodium, but less so with cobalt. Iridium can exist in oxidation states of -III to +V, but iridium(I) and iridium(III) are the more common. iridium(I) compounds (d8 configuration) usually occur with square planar or trigonal bipyramidal geometries, whereas iridium(III) compounds (d6 configuration) typically have an octahedral geometry. Iridium(0) Iridium(0) complexes are binary carbonyls, the principal member being tetrairidium dodecacarbonyl, Ir4(CO)12. Unlike the relate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diene
In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. As a subunit of more complex molecules, dienes occur in naturally occurring and synthetic chemicals and are used in organic synthesis. Conjugated dienes are widely used as monomers in the polymer industry. Polyunsaturated fats are of interest to nutrition. Classes Dienes can be divided into three classes, depending on the relative location of the double bonds: #Cumulated dienes have the double bonds sharing a common atom. The result is more specifically called an allene. #Conjugated dienes have conjugated double bonds separated by one single bond. Conjugated dienes are more stable than other dienes because of resonance. #Unconjugated dienes have the double bonds separated by two or more single bonds. They are usually less stable tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,5-cyclooctadiene
Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula , specifically . There are three configurational isomers with this structure, that differ by the arrangement of the four C–C single bonds adjacent to the double bonds. Each pair of single bonds can be on the same side () or on opposite sides () of the double bond's plane; the three possibilities are denoted , , and ; or (), (), and (). (Because of overall symmetry, is the same configuration as .) Generally abbreviated COD, the isomer of this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry. It is a colorless liquid with a strong odor. 1,5-Cyclooctadiene can be prepared by dimerization of butadiene in the presence of a nickel catalyst, a coproduct being vinylcyclohexene. Approximately 10,000 tons were produced in 2005. Organic reactions COD reacts with borane to give 9-borabicyclo .3.1onane, commonly known as 9-BBN, a reagent in organic chemistr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogeneous Catalysis
In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid-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. Examples Acid catalysis The proton is a pervasive homogeneous catalyst because water is the most common solvent. Water forms protons by the process of self-ionization of water. In an illustrative case, acids accelerate (catalyze) the hydrolysis of esters: :CH3CO2CH3 + H2O CH3CO2H + CH3OH At neutral pH, aqueous solutions of most e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iridium Trichloride
Iridium(III) chloride is the inorganic compound with the formula IrCl3. The anhydrous compound is relatively rare, but the related hydrate is useful for preparing other iridium compounds. The anhydrous salt is a dark green crystalline solid. More commonly encountered is the trihydrate IrCl3(H2O)3. Preparation Iridium is separated from the other platinum group metals as crystalline ammonium hexachloroiridate, (NH4)2 rCl6 which can be reduced to iridium metal in a stream of hydrogen. The spongy Ir thus produced reacts with chlorine at 300–400 °C to give iridium(III) chloride. Hydrated iridium trichloride is obtained by heating hydrated iridium(III) oxide with hydrochloric acid. Structure Like the related rhodium compound, IrCl3 adopts the structure seen for aluminium chloride. This is the monoclinic α polymorph. A rhombohedral β polymorph also exists. Both polymorphs have effectively the same anion lattice but differ in the octahedral interstices the iridium ions o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crabtree's Catalyst
Crabtree's catalyst is an organoiridium compound with the formula [1,5-Cyclooctadiene, C8H12IrTricyclohexylphosphine, P(C6H11)3pyridine, C5H5N]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 complex 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclooctadiene Iridium Methoxide Dimer
Cyclooctadiene iridium methoxide dimer is an organoiridium compound with the formula Ir2(OCH3)2(C8H12)2, where C8H12 is the diene 1,5-cyclooctadiene. It is a yellow solid that is soluble in organic solvents. The complex is used as a precursor to other iridium complexes, some of which are used in homogeneous catalysis In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysi .... The compound is prepared by treating cyclooctadiene iridium chloride dimer with sodium methoxide. In terms of its molecular structure, the iridium centers are square planar as is typical for a d8 complex. The Ir2O2 core is folded. References {{Iridium compounds Homogeneous catalysis Cyclooctadiene complexes Organoiridium compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorobis(cyclooctene)iridium Dimer
Chlorobis(cyclooctene)iridium dimer is an organoiridium compound with the formula Ir2Cl2(C8H14)4, where C8H14 is ''cis''-cyclooctene. Sometimes abbreviated Ir2Cl2(coe)4, it is a yellow, air-sensitive solid that is used as a precursor to many other organoiridium compounds and catalysts. The compound is prepared by heating an alcohol solution of sodium hexachloroiridate with cyclooctene in ethanol. The coe ligands are easily displaced by other more basic ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...s, more so than the diene ligands in the related complex cyclooctadiene iridium chloride dimer. For example, with triphenylphosphine (PPh3), it reacts to give IrCl(PPh3)3: :Ir2Cl2(C8H14)4 + 6 PPh3 → 2 IrCl(PPh3)3 + 4 C8H14 References {{Iridium compounds Organoi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclooctadiene Rhodium Chloride Dimer
Cyclooctadiene rhodium chloride dimer is the organorhodium compound with the formula Rh2Cl2(C8H12)2, commonly abbreviated [RhCl(COD)]2 or Rh2Cl2(COD)2. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalysis, homogeneous catalysts.Giordano, G.; Crabtree, R. H. “Di-μ-chloro-bis(η4-1,5-cyclooctadiene)dirhodium(I)” Inorganic Syntheses, 1990, volume 28, pages 88-90. Preparation and reactions The synthesis of [RhCl(COD)]2 involves heating a solution of hydrated rhodium trichloride with 1,5-cyclooctadiene in aqueous ethanol in the presence of sodium carbonate: :2 RhCl3·3H2O + 2 COD + 2 CH3CH2OH + 2 Na2CO3 → [RhCl(COD)]2 + 2 acetaldehyde, CH3CHO + 8 H2O + 2 CO2 + 4 NaCl [RhCl(COD)]2 is principally used as a source of the electrophile "[Rh(COD)]+." :[RhCl(COD)]2 + L → [LRh(COD)]+Cl− (where L = PR3, alkene, etc. and = 2 or 3) In this way, Chirality (chemistry), chiral phosphines can be attached to Rh. The resulting chiral complexes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogeneous Catalysis
In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid-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. Examples Acid catalysis The proton is a pervasive homogeneous catalyst because water is the most common solvent. Water forms protons by the process of self-ionization of water. In an illustrative case, acids accelerate (catalyze) the hydrolysis of esters: :CH3CO2CH3 + H2O CH3CO2H + CH3OH At neutral pH, aqueous solutions of most e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Complexes
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the Periodic Table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These comple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclooctadiene Complexes
A cyclooctadiene (sometimes abbreviated COD) is any of several cyclic diene with the formula (CH2)4(C2H2)2. Focusing only on cis derivatives, four isomers are possible: 1,2-, which is an allene, 1,3-, 1,4-, and 1,5-. Commonly encountered isomers are the conjugated isomer 1,3-cyclooctadiene and 1,5-cyclooctadiene, which is used as a ligand for transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that ca ...s. These dienes are colorless volatile liquids.Thomas Schiffer, Georg Oenbrink “Cyclododecatriene, Cyclooctadiene, and 4-Vinylcyclohexene” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. References External links1,5-Cyclooctadiene Cycloalkenes Dienes Eight-membered rings {{hydrocarbon-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
