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D Electron Count
The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. The d electron count is an effective way to understand the geometry and reactivity of transition metal complexes. The formalism has been incorporated into the two major models used to describe coordination complexes; crystal field theory and ligand field theory, which is a more advanced version based on molecular orbital theory. Standard electron configuration perspective The electron configuration for transition metals predicted by the simple Aufbau principle and Madelung's rule has serious conflicts with experimental observations for transition metal centers under most ambient conditions. Under most conditions all of the valence electrons of a transition metal center are located in d orbitals while the standard model of electron configuration would predict some of them to be in the pertinent s orbital. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a Chemical reaction, reaction with other Chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahedral Molecular Geometry
In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are cos−1(−) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane () as well as its heavier analogues. Methane and other perfectly symmetrical tetrahedral molecules belong to point group Td, but most tetrahedral molecules have lower symmetry. Tetrahedral molecules can be chiral. Tetrahedral bond angle The bond angle for a symmetric tetrahedral molecule such as CH4 may be calculated using the dot product of two vectors. As shown in the diagram, the molecule can be inscribed in a cube with the tetravalent atom (e.g. carbon) at the cube centre which is the origin of coordinates, O. The four monovalent atoms (e.g. hydrogens) are at four corners of the cube (A, B, C, D) chosen so that no two atoms are at adjacent corners linked by only one cube edge. If the edge length of the cube ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Ferrioxalate
Potassium ferrioxalate, also called potassium trisoxalatoferrate or potassium tris(oxalato)ferrate(III) is a chemical compound with the formula []. It often occurs as the trihydrate . Both are crystalline compounds, lime green in colour.A. Saritha, B. Raju, M. Ramachary, P. Raghavaiah, and K. A. Hussain (2012) "Synthesis, crystal structure and characterization of chiral, three-dimensional anhydrous potassium tris(oxalato)ferrate(III)", ''Physica B: Condensed Matter'', volume 407, issue 21, pages 4208-4213. The compound is a salt consisting of ferrioxalate anions, , and potassium cations . The anion is a transition metal complex consisting of an iron atom in the +3 oxidation state and three bidentate oxalate ions anions acting as ligands. Potassium acts as a counterion, balancing the −3 charge of the complex. In solution, the salt dissociates to give the ferrioxalate anion, []3−, which appears fluorescent green in color. The ferrioxalate anion is quite stable in the dark ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reinecke's Salt
Reinecke's salt is a chemical compound with the formula NH4 r(NCS)4(NH3)2 H2O. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol. The chromium atom is surrounded by six nitrogen atoms in an octahedral geometry. The NH3 ligands are mutually ''trans'' and the Cr–NCS groups are linear. The salt crystallizes with one molecule of water. Structure It was first reported in 1863. NH4 r(NCS)4(NH3)2is prepared by treatment of molten NH4SCN (melting point around 145–150 °C) with (NH4)2Cr2O7. Use This salt was once widely used to precipitate primary and secondary amines as their ammonium salts. Included in the amines that effectively form crystalline precipitates are those derived from the amino acids, including proline and hydroxyproline (2''S'',4''R'')-4-Hydroxyproline, or L-hydroxyproline ( C5 H9 O3 N), is an amino acid, abbreviated as Hyp or O, ''e.g.'', in Protein Data Bank. Structure and discovery In 1902, Hermann Emil Fischer isolated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanocene Dicarbonyl
Dicarbonylbis(cyclopentadienyl)titanium is the chemical compound with the formula (''η''5-C5H5)2Ti(CO)2, abbreviated Cp2Ti(CO)2. This maroon-coloured, air-sensitive species is soluble in aliphatic and aromatic solvents. It has been used for the deoxygenation of sulfoxides, reductive coupling of aromatic aldehydes and reduction of aldehydes. Structure and synthesis Cp2Ti(CO)2 is prepared by the reduction of titanocene dichloride with magnesium as a slurry in THT under an atmosphere of carbon monoxide. :(C5H5)2TiCl2 + Mg + 2 CO → (C5H5)2Ti(CO)2 + MgCl2 Both Cp2Ti(CO)2 and Cp2TiCl2 are tetrahedral as are related zirconium and hafnium compounds. Of historical interest, the complex was first prepared by the reduction of titanocene dichloride with sodium cyclopentadienyl under an atmosphere of carbon monoxide. Its structure has been confirmed by X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadium Tetrachloride
Vanadium tetrachloride is the inorganic compound with the formula V Cl4. This bright red liquid serves as a useful reagent for the preparation of other vanadium compounds. Synthesis, bonding, basic properties With one more valence electron than diamagnetic TiCl4, VCl4 is a paramagnetic liquid. It is one of only a few paramagnetic compounds that is liquid at room temperature. VCl4 is prepared by chlorination of vanadium metal. VCl5 does not form in this reaction; Cl2 lacks the oxidizing power to attack VCl4. VCl5 can however be prepared indirectly from VF5 at −78 °C. In contrast, the heavier analogues NbCl5 and TaCl5 are stable and not particularly oxidizing. VF5 can be prepared directly by fluorination of vanadium metal, reflecting the increased oxidizing power of F2 vs Cl2. Indicative of its oxidizing power, VCl4 releases Cl2 at its boiling point (standard pressure) to afford VCl3. Reactions Consistent with its high oxidizing power, VCl4 reacts with HBr at - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadocene Dichloride
Vanadocene dichloride is an organometallic complex with formula ( ''η''5- C5H5)2VCl2 (commonly abbreviated as Cp2VCl2). It is a structural analogue of titanocene dichloride but with vanadium(IV) instead of titanium(IV). This compound has one unpaired electron, hence Cp2VCl2 is paramagnetic. Vanadocene dichloride is a suitable precursor for variety of bis(cyclopentadienyl)vanadium(IV) compounds. Preparation Cp2VCl2 was first prepared by Wilkinson and Birmingham via the reaction of NaC5H5 and VCl4 in THF. Reactions and use The compound has been used in organic synthesis. Reduction of vanadocene dichloride gives vanadocene, (C5H5)2V. Like titanocene dichloride, this organovanadium compound was investigated as a potential anticancer drug. It was conjectured to function by interactions with the protein transferrin Transferrins are glycoproteins found in vertebrates which bind to and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadyl Acetylacetonate
Vanadyl acetylacetonate is the chemical compound with the formula VO(acac)2, where acac– is the conjugate base of acetylacetone. It is a blue-green solid that dissolves in polar organic solvents. The coordination complex consists of the vanadyl group, VO2+, bound to two acac– ligands via the two oxygen atoms on each. Like other charge-neutral acetylacetonate complexes, it is not soluble in water. Synthesis The complex is generally prepared from vanadium(IV), e.g. vanadyl sulfate: :VOSO4 + 2 Hacac → VO(acac)2 + H2SO4 It can also be prepared by a redox reaction starting with vanadium pentoxide. In this reaction, some acetylacetone is oxidized to acetic anhydride. Structure and properties The complex has a square pyramidal structure with a short V=O bond. This d1 compound is paramagnetic. Its optical spectrum exhibits two transitions. It is a weak Lewis acid, forming adducts with pyridine and methylamine. Applications It is used in organic chemistry as a catalyst for th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum(V) Chloride
Molybdenum(V) chloride is the inorganic compound with the empirical formula . This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents. Structure Usually called molybdenum pentachloride, it is in fact partly a dimer with the molecular formula . In the dimer, each molybdenum has local octahedral symmetry and two chlorides bridge between the molybdenum centers. A similar structure is also found for the pentachlorides of W, Nb and Ta. In the gas phase and partly in solution, the dimers partially dissociate to give a monomeric . The monomer is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is +5, leaving one valence electron on the metal center. Preparation and properties is prepared by chlorination of Mo metal but also chlorination of . The unstable hexachloride is not produced in this way. is reduced by acetonitrile to afford an or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schwartz's Reagent
Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Princeton University.This metallocene is used in organic synthesis for various transformations of alkenes and alkynes. Preparation The complex was first prepared by Wailes and Weigold. It can be purchased or readily prepared by reduction of zirconocene dichloride with lithium aluminium hydride: : (C5H5)2ZrCl2 + LiAlH4 → (C5H5)2ZrHCl + LiAlCl4 This reaction also affords (C5H5)2ZrH2, which is treated with methylene chloride to give Schwartz's reagent LiAl(O-t-Bu)3H can be used in place of LiAlH4. An alternative procedure that generated Schwartz's reagent from dihydride has also been reported. Moreover, it's possible to perform an ''in situ'' preparation of (C5H5)2ZrHCl from zirconocene dichloride by using LiH. This meth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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