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Titanocene
Titanocene dichloride is the organotitanium compound with the formula ( ''η''5-C5H5)2TiCl2, commonly abbreviated as Cp2TiCl2. This metallocene is a common reagent in organometallic and organic synthesis. It exists as a bright red solid that slowly hydrolyzes in air. It shows antitumour activity and was the first non-platinum complex to undergo clinical trials as a chemotherapy drug. Preparation and structure The standard preparations of Cp2TiCl2 start with titanium tetrachloride. The original synthesis by Wilkinson and Birmingham, using sodium cyclopentadienide, is still commonly used: :2 NaC5H5 + TiCl4 → (C5H5)2TiCl2 + 2 NaCl It can also be prepared by using freshly distilled cyclopentadiene rather than its sodium derivative: :2 C5H6 + TiCl4 → (C5H5)2TiCl2 + 2 HCl Focusing on the geometry of the Ti center, Cp2TiCl2 adopts a distorted tetrahedral geometry (counting Cp as a monodentate ligand). The Ti-Cl distance is 2.37 Å and the Cl-Ti-Cl angle is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organotitanium Compound
Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. They are reagents in organic chemistry and are involved in major industrial processes. Brief history Although the first attempt to prepare an organotitanium compound dates back to 1861, the first example was not reported until 1954. In that year titanocene dichloride was described by Wilkinson and Birmingham. Independently, titanium-based Ziegler–Natta catalysts were described leading to major commercial applications, for which the 1963 Nobel Prize in Chemistry was awarded. This technology underscored the technical significance of organotitanium chemistry. Properties The titanium electron configuration ( rd24s2) vaguely resembles that of carbon and like carbon, the +4 oxidation state dominates. Titanium is however a much larger element than carbon, reflect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanocene Pentasulfide
Titanocene pentasulfide is the organotitanium compound with the formula (C5H5)2TiS5, commonly abbreviated as Cp2TiS5. This metallocene exists as a bright red solid that is soluble in organic solvents. It is of academic interest as a precursor to unusual allotropes of elemental sulfur as well as some related inorganic rings. Preparation and structure Titanocene pentasulfide is prepared by treating Cp2TiCl2 with polysulfide salts: It was first produced by the addition of elemental sulfur to titanocene dicarbonyl: :(C5H5)2Ti(CO)2 + S8 → (C5H5)2TiS5 + 2 CO The complex is viewed as a pseudotetrahedral complex of Ti(IV). The Ti–S distances are 2.420 and 2.446 Å and the S–S bond distances are of a normal range, 2.051–2.059 Å. The molecule exhibits a dynamic NMR spectrum owing to the chair–chair equilibrium of the TiS5 ring which equivalizes the Cp signals at high temperatures. Reactions Cp2TiS5 reacts with sulfur and selenium chlorides, E''x''Cl2, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
(Cyclopentadienyl)titanium Trichloride
(Cyclopentadienyl)titanium trichloride is an organotitanium compound with the formula (CH)TiCl. It is a moisture sensitive orange solid. The compound adopts a piano stool geometry. Preparation and reactions (CH)TiCl is prepared by the reaction of titanocene dichloride and titanium tetrachloride Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. is a volatile liquid. Upon contact with humid air, it forms thick clouds ...: :(CH)TiCl + TiCl → 2 (CH)TiCl The complex is electrophilic, readily forming alkoxide complexes upon treatment with alcohols. Reduction of (cyclopentadienyl)titanium trichloride with zinc powder gives the polymeric Ti(III) derivative (cyclopentadienyl)titanium dichloride: :(CH)TiCl + 0.5Zn → 1/n CH)TiCl + 0.5ZnCl See also * (Cyclopentadienyl)zirconium trichloride * (Pentamethylclopentadienyl)titanium trichloride * (Inden ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niobocene Dichloride
Niobocene dichloride is the organometallic compound with the formula (C5H5)2NbCl2, abbreviated Cp2NbCl2. This paramagnetic brown solid is a starting reagent for the synthesis of other organoniobium compounds. The compound adopts a pseudotetrahedral structure with two cyclopentadienyl and two chloride substituents attached to the metal. A variety of similar compounds are known, including Cp2TiCl2. Preparation and structure It was originally reported by Geoffrey Wilkinson. It is prepared via a multistep reaction beginning with treatment of niobium pentachloride with cyclopentadienylsodium: :NbCl5 + 6 NaC5H5 → 5 NaCl + (C5H5)4Nb + organic products :(C5H5)4Nb + 2 HCl + 0.5 O2 → 2O.html" ;"title="sub>2O">sub>2Ol2 + 2 C5H6 :2 HCl + 2O.html" ;"title="sub>2O">sub>2Ol2 + SnCl2 → 2 (C5H5)2NbCl2 + SnCl4 + H2O The compound adopts a "clamshell" structure characteristic of a bent metallocene where the Cp rings are not parallel, the average Cp(centroi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadocene Dichloride
Vanadocene dichloride is an organometallic complex with formula (hapticity, ''η''5-cyclopentadienyl, 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 Geoffrey Wilkinson, Wilkinson and Birmingham via the reaction of NaC5H5 and Vanadium tetrachloride, 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. References {{DEFAULTSORT:Vanadocene Dichloride Metal halides Metallocenes Organovanadium co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tebbe Reagent
Tebbe's reagent is the organometallic compound with the formula (C5H5)2TiCH2ClAl(CH3)2. It is used in the methylenation of carbonyl compounds, that is it converts organic compounds containing the R2C=O group into the related R2C=CH2 derivative. It is a red solid that is pyrophoric in the air, and thus is typically handled with air-free techniques. It was originally synthesized by Fred Tebbe at DuPont Central Research. Tebbe's reagent contains two tetrahedral metal centers linked by a pair of bridging ligands. The titanium has two cyclopentadienyl (, or Cp) rings and aluminium has two methyl groups. The titanium and aluminium atoms are linked together by both a methylene bridge (-CH2-) and a chloride atom in a nearly square-planar (Ti–CH2–Al–Cl) geometry. The Tebbe reagent was the first reported compound where a methylene bridge connects a transition metal (Ti) and a main group metal (Al).Herrmann, W.A., "The Methylene Bridge" ''Advances in Organometallic Chemistry'' 1982, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdocene Dichloride
Molybdocene dichloride is the organomolybdenum compound with the formula ( η5-C5H5)2MoCl2 and IUPAC name dichlorobis(η5-cyclopentadienyl)molybdenum(IV), and is commonly abbreviated as Cp2MoCl2. It is a brownish-green air- and moisture-sensitive powder. In the research laboratory, it is used to prepare many derivatives. Preparation and structure The compound is prepared from molybdocene dihydride Molybdocene dihydride is the organomolybdenum compound with the formula ( η5-C5H5)2MoH2. Commonly abbreviated as Cp2MoH2, it is a yellow air-sensitive solid that dissolves in some organic solvents. The compound is prepared by combining molybde ... by treatment with chloroform: :(C5H5)2MoH2 + 2 CHCl3 → (C5H5)2MoCl2 + 2 CH2Cl2 The compound adopts a "clamshell" structure where the Cp rings are not parallel, the average Cp(centroid)-M-Cp angle being 130.6°. The two chloride ligands are cis, the Cl-Mo-Cl angle of 82° being narrower than in niobocene dichloride (85.6°), which in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconocene Dichloride
Zirconocene dichloride is an organozirconium compound composed of a zirconium central atom, with two cyclopentadienyl and two chloro ligands. It is a colourless diamagnetic solid that is somewhat stable in air. Preparation and structure Zirconocene dichloride may be prepared from zirconium(IV) chloride-THF complex and sodium cyclopentadienide: :ZrCl4(THF)2 + 2 NaCp → Cp2ZrCl2 + 2 NaCl + 2 THF The closely related compound Cp2ZrBr2 was first described by Birmingham and Wilkinson. The compound is a bent metallocene: the Cp rings are not parallel, the average Cp(centroid)-M-Cp angle being 128°. The Cl-Zr-Cl angle of 97.1° is wider than in niobocene dichloride (85.6°) and molybdocene dichloride (82°). This trend helped to establish the orientation of the HOMO in this class of complex. Reactions Schwartz's reagent Zirconocene dichloride reacts with lithium aluminium hydride to give Cp2ZrHCl Schwartz's reagent: :(C5H5)2ZrCl2 + 1/4 LiAlH4 → (C5H5)2ZrHCl + 1/4 LiAlCl4 Since ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petasis Reagent
The Petasis reagent, named after Nicos A. Petasis, is an organotitanium compound with the formula Cp2Ti(CH3)2. It is an orange-colored solid. Preparation and use The Petasis reagent is prepared by the salt metathesis reaction of methylmagnesium chloride or methyllithium with titanocene dichloride: : Cp2TiCl2 + 2 CH3MgCl → Cp2Ti(CH3)2 + 2 MgCl2 This compound is used for the transformation of carbonyl groups to terminal alkenes. It exhibits similar reactivity to the Tebbe reagent and Wittig reaction. Unlike the Wittig reaction, the Petasis reagent can react with a wide range of aldehydes, ketones and esters. The Petasis reagent is also very air stable, and is commonly used in solution with toluene or THF. The Tebbe reagent and the Petasis reagent share a similar reaction mechanism. The active olefinating reagent, Cp2TiCH2, is generated in situ upon heating. With the organic carbonyl, this titanium carbene forms a four membered oxatitanacyclobutane that releases the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferrocene
Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, and is soluble in most organic solvents. It is remarkable for its stability: it is unaffected by air, water, strong bases, and can be heated to 400 °C without decomposition. In oxidizing conditions it can reversibly react with strong acids to form the ferrocenium cation . The rapid growth of organometallic chemistry is often attributed to the excitement arising from the discovery of ferrocene and its many analogues, such as metallocenes. History Discovery Ferrocene was discovered by accident thrice. The first known synthesis may have been made in the late 1940s by unknown researchers at Union Carbide, who tried to pass hot cyclopentadiene vapor through an iron pipe. The vapor reacted with the pipe wall, creating a "yellow slu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. History The terms ''nucleophile'' and '' electrophile'' were introduced by Christopher Kelk Ingold in 1933, replacing the terms ''anionoid'' and ''catio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Hydrosulfide
Sodium hydrosulfide is the chemical compound with the formula NaHS. This compound is the product of the half-neutralization of hydrogen sulfide () with sodium hydroxide (NaOH). NaSH and sodium sulfide are used industrially, often for similar purposes. Solid NaSH is colorless. The solid has an odor of owing to hydrolysis by atmospheric moisture. In contrast with sodium sulfide (), which is insoluble in organic solvents, NaSH, being a 1:1 electrolyte, is more soluble. Structure and properties Crystalline NaHS undergoes two phase transitions. At temperatures above 360 K, NaSH adopts the NaCl structure, which implies that the behaves as a spherical anion owing to its rapid rotation, leading to equal occupancy of eight equivalent positions. Below 360 K, a rhombohedral structure forms, and the sweeps out a discoidal shape. Below 114 K, the structure becomes monoclinic. The analogous rubidium and potassium compounds behave similarly. NaSH has a relatively low melting poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
