|
Hafnium Acetylacetonate
Hafnium acetylacetonate, also known as Hf(acac)4, is a coordination compound with formula Hf(C5H7O2)4. This white solid is the main hafnium complex of acetylacetonate. The complex has a square antiprismatic geometry with eight nearly equivalent Hf-O bonds. The molecular symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ... is ''D''2, i.e., the complex is chiral. It is prepared from hafnium tetrachloride and acetylacetone, and base. Zr(acac)4 is very similar in structure and properties. Uses Along with titanium tetrabutoxide (TBT), hafnium acetylacetonate serves as a catalyst for the production of poly(butylene terephthalate). Related compounds *Tetrakis(1,1,1-trifluoro-2,4-pentanedionato)hafnium References {{organic-compound-stub Hafnium compounds Acetylacetonate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Elements
American Elements is a global manufacturer and distributor of advanced materials with a more than 35,000-page online product catalog and compendium of information on the chemical elements, advanced materials, and high technology applications. The company's headquarters and educational programs are based in Los Angeles, California. Its research and production facilities are located in Salt Lake City, Utah; Monterrey, Mexico; Baotou, China; and Manchester, UK. History American Elements began as a toll chemical manufacturer and refiner serving U.S. mining companies by producing metal-based chemicals from their deposits. In 1998, its two largest customers, the Unocal/Molycorp rare-earth mine in Mountain Pass, California and the Rhodia rare-earth refinery in Freeport, Texas closed, ending domestic U.S. rare-earth production. In response, the company established mining joint ventures in Inner Mongolia, China and in 1999 became one of the first post-Cold War companies to export rare-eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Compound
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] |
Hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Dirk Coster and George de Hevesy, making it the penultimate stable element to be discovered (the last being rhenium in 1925). Hafnium is named after , the Latin name for Copenhagen, where it was discovered. Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nanometers and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten. Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetylacetonate
Acetylacetone is an organic compound with the chemical formula . It is a colorless liquid, classified as a 1,3-diketone. It exists in equilibrium with a tautomer . These tautomers interconvert so rapidly under most conditions that they are treated as a single compound in most applications. It is a colorless liquid that is a precursor to acetylacetonate anion (commonly abbreviated acac−), a bidentate ligand. It is also a building block for the synthesis of heterocyclic compounds. Properties Tautomerism The keto and enol tautomers of acetylacetone coexist in solution. The enol form has C2v symmetry, meaning the hydrogen atom is shared equally between the two oxygen atoms. In the gas phase, the equilibrium constant, ''K''keto→enol, is 11.7, favoring the enol form. The two tautomeric forms can be distinguished by NMR spectroscopy, IR spectroscopy and other methods. The equilibrium constant tends to be high in nonpolar solvents; when k = >1, the enol form is favour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiprism
In geometry, an antiprism or is a polyhedron composed of two parallel direct copies (not mirror images) of an polygon, connected by an alternating band of triangles. They are represented by the Conway notation . Antiprisms are a subclass of prismatoids, and are a (degenerate) type of snub polyhedron. Antiprisms are similar to prisms, except that the bases are twisted relatively to each other, and that the side faces (connecting the bases) are triangles, rather than quadrilaterals. The dual polyhedron of an -gonal antiprism is an -gonal trapezohedron. History At the intersection of modern-day graph theory and coding theory, the triangulation of a set of points have interested mathematicians since Isaac Newton, who fruitlessly sought a mathematical proof of the kissing number problem in 1694. The existence of antiprisms was discussed, and their name was coined by Johannes Kepler, though it is possible that they were previously known to Archimedes, as they satisfy the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symmetry Group
In group theory, the symmetry group of a geometric object is the group of all transformations under which the object is invariant, endowed with the group operation of composition. Such a transformation is an invertible mapping of the ambient space which takes the object to itself, and which preserves all the relevant structure of the object. A frequent notation for the symmetry group of an object ''X'' is ''G'' = Sym(''X''). For an object in a metric space, its symmetries form a subgroup of the isometry group of the ambient space. This article mainly considers symmetry groups in Euclidean geometry, but the concept may also be studied for more general types of geometric structure. Introduction We consider the "objects" possessing symmetry to be geometric figures, images, and patterns, such as a wallpaper pattern. For symmetry of physical objects, one may also take their physical composition as part of the pattern. (A pattern may be specified formally as a scalar field, a funct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconium Acetylacetonate
Zirconium acetylacetonate is the coordination complex with the formula Zr(C5H7O2)4. It is a common acetylacetonate of zirconium. It is a white solid that exhibits high solubility in nonpolar organic solvents, but not simple hydrocarbons. The complex is prepared by treating zirconium oxychloride with acetylacetone: :ZrOCl2 + 4 Hacac → Zr(acac)4 + 2 HCl + H2O The complex has a square antiprismatic geometry with eight nearly equivalent Zr-O bonds of length 2.19 Å. The molecular symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definiti ... is D2, i.e. the complex is chiral. Compounds of high coordination number tend to be stereochemically nonrigid as indicated by the observation of one methyl signal by proton NMR spectroscopy. More volatile than Zr(acac)4 is the relate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Catalysis is ubiquitous in chemical industry of all kinds. Estimates are that 90% of all commercially produced chemical products involve catalysts at some s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium Compounds
Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known. Halides Hafnium(IV) fluoride (HfF4) is a white crystalline powder. It has a monoclinic crystal structure, with space group C2/c (No.15), and lattice constants ''a'' = 1.17 nm, ''b'' = 0.986 nm and ''c'' = 0.764 nm. Hafnium(IV) c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_oxide.jpg "Click for more on -> Hafnium Compounds")