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Titanocene Dichloride
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 9 ... [...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 sludg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Cyclopentadienide
Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp, where Cp− is the cyclopentadienide anion. Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities. Preparation Sodium cyclopentadienide is commercially available as a solution in THF. It is prepared by treating cyclopentadiene with sodium: : The conversion can be conducted by heating a suspension of molten sodium in dicyclopentadiene.Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878. In former times, the sodium was provided in the form of "sodium wire" or "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing xylene and rapidly stirring. Sodium hydride is a convenient base: : In early work, Grignard reagents were used as bases. With a p''K''a of 15, cyclopen ... [...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] |
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] |
Justus Liebigs Ann
Justus (died on 10 November between 627 and 631) was the fourth Archbishop of Canterbury. He was sent from Italy to England by Pope Gregory the Great, on a mission to Christianize the Anglo-Saxons from their native paganism, probably arriving with the second group of missionaries despatched in 601. Justus became the first Bishop of Rochester in 604, and attended a church council in Paris in 614. Following the death of King Æthelberht of Kent in 616, Justus was forced to flee to Gaul, but was reinstated in his diocese the following year. In 624 Justus became Archbishop of Canterbury, overseeing the despatch of missionaries to Northumbria. After his death he was revered as a saint, and had a shrine in St Augustine's Abbey, Canterbury. Arrival in Britain Justus was a member of the Gregorian mission sent to England by Pope Gregory I. Almost everything known about Justus and his career is derived from the early 8th-century ''Historia ecclesiastica gentis Anglorum'' of Bede ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methyllithium
Methyllithium is the simplest organolithium reagent with the empirical formula CH3Li. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used in solution with an ether as the solvent, is a reagent in organic synthesis as well as organometallic chemistry. Operations involving methyllithium require anhydrous conditions, because the compound is highly reactive toward water. Oxygen and carbon dioxide are also incompatible with MeLi. Methyllithium is usually not prepared, but purchased as a solution in various ethers. Synthesis In the direct synthesis, methyl bromide is treated with a suspension of lithium in diethyl ether. :2 Li + MeBr → LiMe + LiBr The lithium bromide forms a complex with the methyllithium. Most commercially available methyllithium consists of this complex. "Halide-free" methyllithium is prepared from methyl chloride. Lithium chloride precipitates from the diethyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylmagnesium Chloride
Methylmagnesium chloride is an organometallic compound with the general formula CH3MgCl. This highly flammable, colorless, and moisture sensitive material is the simplest Grignard reagent and is commercially available, usually as a solution in tetrahydrofuran. Synthesis and reactions Relative to the more commonly encountered methylmagnesium bromide and methylmagnesium iodide, methylmagnesium chloride offers the advantages of low equivalent weight and low cost. It is prepared by the reaction of methyl chloride and magnesium in ethyl ether. left, Structure of CH3MgCl(thf)2, which is representative of the species in donor solvents. As with most Grignard reagents, methylmagnesium chloride is highly solvated by ether solvents via coordination from two oxygen atoms to give a tetrahedrally bonded magnesium center. Like methyllithium, it is the synthetic equivalent to the methyl carbanion synthon. It reacts with water and other protic reagents to give methane, e.g.,: :CH3MgCl + ... [...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 te ... [...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, to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polysulfide
Polysulfides are a class of chemical compounds containing chains of sulfur atoms. There are two main classes of polysulfides: inorganic and organic. Among the inorganic polysulfides, there are ones which contain anions, which have the general formula . These anions are the conjugate bases of the hydrogen polysulfides . Organic polysulfides generally have the formulae , where R = alkyl or aryl. Polysulfide salts and complexes The alkali metal polysulfides arise by treatment of a solution of sulfide, e.g. sodium sulfide, with elemental sulfur: : In some cases, these anions have been obtained as organic salts, which are soluble in organic solvents. The energy released in the reaction of sodium and elemental sulfur is the basis of battery technology. The sodium–sulfur battery and the lithium–sulfur battery require high temperatures to maintain liquid polysulfide and -conductive membranes that are unreactive toward sodium, sulfur, and sodium sulfide. Polysulfides are ligands i ... [...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] |
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 ''cationoid' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
