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Hexa(tert-butoxy)ditungsten(III)
Hexa(''tert''-butoxy)ditungsten(III) is a coordination complex of tungsten(III). It is one of the homoleptic alkoxides of tungsten. A red, air-sensitive solid, the complex has attracted academic attention as the precursor to many organotungsten derivatives. It an example of a charge-neutral complex featuring a W≡W bond, arising from the coupling of a pair of d3 metal centers. It has attracted particular attention for its reactions with alkynes, leading to alkyne metathesis. It can be prepared by the salt metathesis reaction from the thf complex of ditungsten heptachloride: :NaW2Cl7(THF)5 + 6 NaOBu-t → W2(OBu-t)6 + 7 NaCl + 5 THF It was originally prepared by alcoholysis of the amide W2(NMe2)6. The complex and its dimolybdenum analogue adopt a staggered, ethane-like conformation. The M-M distance is 233 pm. The complex is a weak Lewis acid, forming adducts with two pyridine ligands, for example.{{cite journal , doi=10.1016/S0277-5387(97)00290-8, title=Pyridine, is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexa(tert-butoxy)dimolybdenum(III)
Hexa(''tert''-butoxy)dimolybdenum(III) is a coordination complex of molybdenum(III). It is one of the homoleptic alkoxides of molybdenum. An orange, air-sensitive solid, the complex has attracted academic attention as the precursor to many organomolybdenum derivatives. It an example of a charge-neutral complex featuring a molybdenum to molybdenum triple bond (Mo≡Mo), arising from the coupling of a pair of d3 metal centers. It can be prepared by a salt metathesis reaction from the THF complex of molybdenum trichloride and lithium tert-butoxide: :2 MoCl3(thf)3 + 6 LiOBu-t → Mo2(OBu-t)6 + 6 LiCl + 6 thf The complex and its ditungsten (W2) analogue adopt an ethane-like geometry. The metal to metal bond distance is 222 pm in the related complex Mo2(OCH2CMe3)6.{{cite journal , doi=10.1021/ic50173a045, title=The molybdenum-molybdenum triple bond. 2. Hexakis(alkoxy)dimolybdenum compounds: Preparation, properties and structural characterization of hexakis(neopentoxy)dimo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Complex
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 compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homoleptic
In inorganic chemistry, a homoleptic chemical compound is a metal compound with all ligands identical. The term uses the " homo-" prefix to indicate that something is the same for all. Any metal species which has more than one type of ligand is heteroleptic. Some compounds with names that suggest that they are homoleptic are in fact heteroleptic, because they have ligands in them which are not featured in the name. For instance dialkyl magnesium complexes, which are found in the equilibrium which exists in a solution of a Grignard reagent in an ether, have two ether ligands attached to each magnesium centre. Another example is a solution of trimethyl aluminium in an ether solvent (such as THF); similar chemistry should be expected for a triaryl or trialkyl borane. It is possible for some ligands such as DMSO to bind with two or more different coordination modes. It would still be reasonable to consider a complex which has only one type of ligand but with different coordination m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts. Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols. Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a derivative of be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organotungsten Chemistry
Organomolybdenum chemistry is the chemistry of chemical compounds with Mo-C bonds. The heavier group 6 elements molybdenum and tungsten form organometallic compounds similar to those in organochromium chemistry but higher oxidation states tend to be more common. Mo(0) and more reduced states Molybdenum hexacarbonyl is the precursor to many substituted derivatives. It reacts with organolithium reagents to give anionic acyls which can be O-alkylated to give Fischer carbenes. 144px, Structure of (mesitylene)molybdenum tricarbonyl. Mo(CO)6 reacts with arenes to give piano-stool complexes such as (mesitylene)molybdenum tricarbonyl. Cycloheptatrienemolybdenum tricarbonyl, which is related to (arene)Mo(CO)3, reacts with trityl salts to give the cycloheptatrienyl complex: :(C7H8)Mo(CO)3 + (C6H5)3C+ → C7H7)Mo(CO)3sup>+ + (C6H5)3CH file:CHTMo(CO)3.png, 144px, Structure of Cycloheptatrienemolybdenum tricarbonyl. Reduction of Mo(CO)6 gives [Mo(CO)5]2− which is formally Mo(-II ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyne Metathesis
Alkyne metathesis is an organic reaction that entails the redistribution of alkyne chemical bonds. The reaction requires metal catalysts. Mechanistic studies show that the conversion proceeds via the intermediacy of metal alkylidyne complexes. The reaction is related to olefin metathesis. History Metal-catalyzed alkyne metathesis was first described in 1968 by Bailey, et al. The Bailey system utilized a mixture of tungsten and silicon oxides at temperatures as high as 450 °C. In 1974 Mortreux reported the use of a homogeneous catalyst—molybdenum hexacarbonyl at 160 °C—to observe an alkyne scrambling phenomenon, in which an unsymmetrical alkyne equilibrates with its two symmetrical derivatives. The Mortreux system consists of the molybdenum precatalyst molybdenum hexacarbonyl Mo(CO)6 and resorcinol cocatalyst. In 1975, T. J. Katz proposed a metal carbyne (i.e. alkylidyne) and a metallacyclobutadiene as intermediates. In 1981, R. R. Schrock characterized severa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkoxides
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts. Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols. Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a derivative o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
