Search results for "Potassium"
showing 10 items of 930 documents
Combining Neopentyllithium with Potassium tert-Butoxide: Formation of an Alkane-Soluble Lochmann-Schlosser Superbase.
2016
Mixtures of alkyllithium and heavier alkali-metal alkoxides are often used to form alkyl compounds of heavier alkali metals, but these mixtures are also known for their high reactivity in deprotonative metalation reactions. These organometallic mixtures are often called LiC-KOR superbases, but despite many efforts their constitution remains unknown. Herein we present mixed alkali-metal alkyl/alkoxy compounds produced by reaction of neopentyllithium with potassium tert-butoxide. The key to success was the good solubility and temperature-stability of neopentyl alkali-metal compounds, leading to hexane-soluble mixtures, which allowed handling at ambient temperatures and isolation by crystalliz…
Towards the Next Generation of Lochmann-Schlosser Superbases: A Potassium Neopentyl/Alkoxy Aggregate used in the Tetra-Functionalization of Ferrocene
2018
Lochmann-Schlosser superbases are formed by mixing alkyllithium with potassium alkoxides. These reagents could prove their synthetic usefulness and reliability in many reactions over five decades. However, despite many efforts, the real source of the exceptional reactivity remained a secret. The seemingly manageable system of four components (lithium, potassium atoms, alkyl groups, and alkoxy groups) and their interaction is obscured by poor solubility and fierce reactivity. Recent progress was achieved by using neopentyllithium, leading to alkane-soluble aggregates with varying lithium/potassium content and a flexible alkyl/alkoxy ratio. Herein, we isolated two new alkane-soluble alkyl/alk…
Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers
2012
In the search for new ligands for the Ullmann diaryl ether synthesis, permitting the coupling of electron-rich aryl bromides at relatively low temperatures, 56 structurally diverse multidentate ligands were screened in a model system that uses copper iodide in acetonitrile with potassium phosphate as the base. The ligands differed largely in their performance, but no privileged structural class could be identified.
Chemistry of the μ-hydridobis(pentacarbonylchromium(0)) species
1977
Abstract Reactions of the potassium and tetrabutylammonium derivatives of Cr 2 H(CO) 10 − , with N-donor bidentate ligands such as 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) have been investigated. A coordination compound of general formula K[Cr 2 H(CO) 10 (phen) 3 ] is the most stable product from the reaction of the former with phen, but under certain conditions a 1 2 adduct may also be isolated. The analogous reaction with bpy leads to a single labile adduct, K[Cr 2 H(CO) 10 (bpy) 2 ]. (C 4 H 9 ) 4 N[Cr 2 H(CO) 10 (phen)] is formed by interaction of the latter derivative with phen, but bpy does not give the analogous adduct.
Selective Guest Inclusion in Oxalate-Based Iron(III) Magnetic Coordination Polymers
2016
The preparation and structural characterization of four novel oxalate-based iron(III) compounds of formulas {(MeNH3)2[Fe2(ox)2Cl4]·2.5H2O}n (1), K(MeNH3)[Fe(ox)Cl3(H2O)] (2), {MeNH3[Fe2(OH)(ox)2Cl2]·2H2O}n (3), and {(H3O)(MeNH3)[Fe2O(ox)2Cl2]·3H2O}n (4) (MeNH3+ = methylammonium cation and H2ox = oxalic acid) are reported here. 1 is an anionic waving chain of oxalato-bridged iron(III) ions with peripheral chloro ligands, the charge balance being ensured by methylammonium cations. 2 is a mononuclear complex with a bidentate oxalate, three terminal chloro ligands, and a coordinated water molecule achieving the six-coordination around each iron(III) ion. Its negative charge is balanced by potas…
Apparent molar volumes of potassium nitrate and sodium nitrate in ethanol + water at 298.15 K
1998
Densities of ethanol + water + potassium nitrate and ethanol + water + sodium nitrate mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of the salt and ethanol, at 298.15 K. From these densities, apparent molar volumes of both electrolytes in ethanol + water mixtures have been calculated, and partial molar volumes at infinite dilution have been evaluated.
Über die reduktion von polyacrylsäurederivaten
1960
Bei der Reduktion von Polyacrylsaurechlorid und von Polyacrylsaure-N-methylanilid mit Lithiumaluminium-tri-tert.-butoxyhydrid bzw. Lithiumaluminiumhydrid entstehen Polymere mit 30–50 Mol-% Aldehydgruppen. Aus Polyacrylsaurechloriden, Polyacrylsauremethylestern und Polyacroleinen wurden bei der Reduktion mit Lithiumaluminiumhydrid bzw. Kaliumborhydrid identische polymere Allylalkohole erhalten. Diese lassen sich acylieren, tritylieren und tosylieren. Die Polyallyl- und Polyvinyl-dinitrobenzoate bilden mit α-Naphthylamin und Benzidin gefaurbte Molekulverbindungen. The reduction of polyacrylyl chloride and polyacryl-N-methylanilide with lithium aluminum tri-tert-butoxyhydride and lithium alumi…
Cyclodextrins in polymer synthesis: free radical polymerisation of cyclodextrin complexes of cyclohexyl and phenyl methacrylate in aqueous medium
1998
The polymerisation mechanism of 2,6-dimethyl-β-cyclodextrin (Me2-β-CD) complexes of phenyl methacrylate (1) and cyclohexyl methacrylate (2) is described. The polymerisation of the complexes 1 a and 2a was carried out in water with potassium peroxodisulfate/potassium hydrogensulfite as initiator. The unthreading of the Me2-β-CD during the polymerisation led to water-insoluble poly(phenyl methacrylate) (1b) and poly(cyclohexyl methacrylate) (2b). By comparison, analogously prepared polymers from uncomplexed monomers 1 and 2 in homogeneous organic solvent (THF) with AIBN as radical initiator showed significantly lower viscosities and were obtained in lower yields in both cases.
Electron-transfer reduction of selected alcohols with alkalide K−, K+(15-crown-5)2 via organometallic intermediates
2004
Abstract The course of the reaction of alkalide K − , K + (15-crown-5) 2 1 with selected alcohols depends on the kind of alcohol and the mode of substrate delivery. In the case of methanol, potassium methoxide formed initially undergoes destruction at the excess of 1 . It results in potassium oxide and methylpotassium. The latter opens the crown ether ring giving potassium tetraethylene glycoxide vinyl ether and methane. A similar course of the process is observed for propanol. Potassium glycidoxide is the main product formed in the reaction of 1 with glycidol. Its oxirane ring is opened at the excess of 1 . Organopotassium alkoxides, i.e., potassium potassiomethoxide and dipotassium potass…
Ion pair association in isodielectric mixtures at 25�C
1974
Conductance measurements of potassium perchlorate and iodide have been carried out on the following mixtures: methanol-ethylene carbonate, acetone-ethylene carbonate, acetonitrile-ethylene carbonate, sulfolane-ethylene carbonate, isodielectric with water; and in benzene-sulfolane, benzene-acetonitrile, ethanol-sulfolane, isodielectric with methanol. The extent of ionic association at a given concentration in two solvents of the same dielectric constant is greater in the aprotic solvent.