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Transition Metal Dinitrogen Complex
Transition metal dinitrogen complexes are coordination compounds that contain transition metals as ion centers the Nitrogen, dinitrogen molecules (N2) as ligands. Historical background Transition metal complexes of N2 have been studied since 1965 when the first complex was reported by Allen and Senoff. This Diamagnetism, diamagnetic complex, Pentaamine(nitrogen)ruthenium(II) chloride, [Ru(NH3)5(N2)]2+, was synthesized from hydrazine hydrate and ruthenium trichloride and consists of a [Ru(NH3)5]2+ centre attached to one end of N2. The existence of N2 as a ligand in this compound was identified by IR spectrum with a strong band around 2170–2100 cm−1. In 1966, the molecular structure of [Ru(NH3)5(N2)]Cl2 was determined by Bottomly and Nyburg by X-ray crystallography. The dinitrogen complex ''trans''-[IrCl(N2)(PPh3)2] is made by treating Vaska's complex with aromatic acyl azides. It has a planar geometry. The first preparation of a metal-dinitrogen complex using dinitro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Transfer
Electron transfer (ET) occurs when an electron relocates from an atom, ion, or molecule, to another such chemical entity. ET describes the mechanism by which electrons are transferred in redox reactions. Electrochemical processes are ET reactions. ET reactions are relevant to photosynthesis and respiration and commonly involve transition metal complexes. In organic chemistry ET is a step in some industrial polymerization reactions. It is foundational to photoredox catalysis. Classes of electron transfer Inner-sphere electron transfer In inner-sphere ET, two redox centers are covalently linked during the ET. This bridge can be permanent, in which case the electron transfer event is termed intramolecular electron transfer. More commonly, however, the covalent linkage is transitory, forming just prior to the ET and then disconnecting following the ET event. In such cases, the electron transfer is termed intermolecular electron transfer. A famous example of an inner sphere ET pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abiological Nitrogen Fixation
Abiological nitrogen fixation describes chemical processes that fix (react with) N2, usually with the goal of generating ammonia. The dominant technology for abiological nitrogen fixation is the Haber process, which uses iron-based heterogeneous catalysts and H2 to convert N2 to NH3. This article focuses on homogeneous (soluble) catalysts for the same or similar conversions. Transition metals Vol'pin and Shur An early influential discovery of abiological nitrogen fixation was made by Vol'pin and co-workers in Russia in 1970. Aspects are described in an early review: "using a non-protic Lewis acid, aluminium tribromide, were able to demonstrate the truly catalytic effect of titanium by treating dinitrogen with a mixture of titanium tetrachloride, metallic aluminium, and aluminium tribromide at 50 °C, either in the absence or in the presence of a solvent, e.g. benzene. As much as 200 mol of ammonia per mol of was obtained after hydrolysis.…" These results led to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. It is widely used in fertilizers, refrigerants, explosives, cleaning agents, and is a precursor for numeous chemicals. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil. Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals. In many countries, it is classified as an List of extremely hazardous substances, extremely hazardous substance. Ammonia is toxic, cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abiological Nitrogen Fixation
Abiological nitrogen fixation describes chemical processes that fix (react with) N2, usually with the goal of generating ammonia. The dominant technology for abiological nitrogen fixation is the Haber process, which uses iron-based heterogeneous catalysts and H2 to convert N2 to NH3. This article focuses on homogeneous (soluble) catalysts for the same or similar conversions. Transition metals Vol'pin and Shur An early influential discovery of abiological nitrogen fixation was made by Vol'pin and co-workers in Russia in 1970. Aspects are described in an early review: "using a non-protic Lewis acid, aluminium tribromide, were able to demonstrate the truly catalytic effect of titanium by treating dinitrogen with a mixture of titanium tetrachloride, metallic aluminium, and aluminium tribromide at 50 °C, either in the absence or in the presence of a solvent, e.g. benzene. As much as 200 mol of ammonia per mol of was obtained after hydrolysis.…" These results led to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal 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 f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hapticity
In coordination chemistry, hapticity is the coordination complex, coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter eta (letter), η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated (otherwise the denticity, κ-notation is used). In addition, if the ligand coordinates through multiple atoms that are contiguous then this is considered denticity (not hapticity), and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with mu (letter), μ ('mu'), which relates to bridging ligands. History The need for additional nomenclature for organometallic compounds became apparent in the mid-1950s when Dunitz, Leslie Orgel, Orgel, and Rich described the structure of the "sandwich compound, sandwich complex" ferrocene by X-ray ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bridging Ligand
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals. In naming a complex wherein a single atom bridges two metals, the bridging ligand is preceded by the Greek letter mu, μ, with a subscript number denoting the number of metals bound to the bridging ligand. μ2 is often denoted simply as μ. When describing coordination complexes care should be taken not to confuse μ with η ('eta'), which relates to hapticity. Ligands that are not bridging are called terminal ligands. List of bridging ligands Virtually all ligands are known to bridge, with the exception of amines and ammonia. Common bridging ligands include most of the common anions. Many simple organic ligands form s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition State
In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked with the double dagger (‡) symbol. As an example, the transition state shown below occurs during the SN2 reaction of bromoethane with a hydroxide anion: The activated complex of a reaction can refer to either the transition state or to other states along the reaction coordinate between reactants and products, especially those close to the transition state. Peter Atkins and Julio de Paula, ''Physical Chemistry'' (8th ed., W.H. Freeman 2006), p.809 According to the transition state theory, once the reactants have passed through the transition state configuration, they always continue to form products. History of concept The concept of a transition state has been important in many theories of the rates at which chemical re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bis(dinitrogen)bis(1,2-bis(diphenylphosphino)ethane)molybdenum(0)
''trans''-Bis(dinitrogen)bis ,2-bis(diphenylphosphino)ethaneolybdenum(0) is a coordination complex with the formula Mo(N2)2(dppe)2. It is a relatively air stable yellow-orange solid. It is notable as being the first discovered dinitrogen containing complex of molybdenum. Structure Mo(N2)2(dppe)2 is an octahedral complex with idealized D2h point group symmetry. The dinitrogen ligands are mutually trans across the metal center. The Mo-N bond has a length of 2.01 Å, and the N-N bond has a length of 1.10 Å. This length is close to the free nitrogen bond length, but coordination to the metal weakens the N-N bond making it susceptible to electrophilic attack. Synthesis The first synthetic route to Mo(N2)2(DPPE)2 involved a reduction of molybdenum(III) acetylacetonate with triethylaluminium in the presence of dppe and nitrogen. A higher yielding synthesis involves a four-step process. In the first step, molybdenum(V) chloride is reduced by acetonitrile (CH3CN) to give oCl4(CH3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triple Bond
A triple bond in chemistry is a chemical bond between two atoms involving six Electron pair bond, bonding electrons instead of the usual two in a covalent bond, covalent single bond. Triple bonds are stronger than the equivalent covalent bond, single bonds or double bond, double bonds, with a bond order of three. The most common triple bond is in a nitrogen N2 molecule; the second most common is that between two carbon atoms, which can be found in alkynes. Other functional groups containing a triple bond are cyanides and isocyanides. Some diatomic molecules, such as diphosphorus and carbon monoxide, are also triple bonded. In skeletal formula, skeletal formulae the triple bond is drawn as three parallel lines (≡) between the two connected atoms. Bonding Triple bonding can be explained in terms of orbital hybridization. In the case of acetylene, each carbon atom has two sp orbital, sp-orbitals and two p-orbitals. The two sp-orbitals are linear, with 180° bond angles, and occupy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
