Metal-Fluorocarbon Solvents

Brennessel, W. W. et al., J. Amer. Chem. Soc., 2002, 124(35), 10258 Pyrophoric, and spontaneously ignites with fluorocarbon solvents even under argon. See also METAL DERIVATIVES OF ORGANOFLUORINE COMPOUNDS See other ORGANOMETALLICS... 

Flash-photolysis studies of the hexacarbonyls Cr(CO)g, Mo(CO)g and W(CO)g are, like previous years, still abundant Nayak and Burkey have found that there are low quantum yields for Cr(CO)g substitution in fluorocarbon solvents - which provides yet more evidence that metal-fluorocarbon interactions are very weak There have been estimates made of solvent-metal bond strengths in (Solvent)M(CO)5 complexes (Solvent = Benzene [M = Mo, W] and Tetrachloromethane [M = Cr]) and the photolysis of W(CO)g in the presence of hex-l-ene has been reported Flash-photolysis studies of the photochemical reactions of silanes with Cr(CO)g have been published Using time-resolved infrared spectroscopy RIR), Turner and co-workers have captured the IR spectrum of the MLCT excited state of W(CO)5(4-cyanopyridine) which rapidly decays to W(CO)5. The excited state of W(CO)5(4-cyanopyridine) is relatively long lived, which makes the experiment possible. This reporter will be interested to see how this technique develops. 

Surfactants and Colloids in Supercritical Fluids Because very few nonvolatile molecules are soluble in CO2, many types of hydrophilic or lipophilic species may be dispersed in the form of polymer latexes (e.g., polystyrene), microemulsions, macroemulsions, and inorganic suspensions of metals and metal oxides (Shah et al., op. cit.). The environmentally benign, nontoxic, and nonflammable fluids water and CO2 are the two most abundant and inexpensive solvents on earth. Fluorocarbon and hydrocarbon-based surfactants have been used to form reverse micelles, water-in-C02... 

D. Fluorocarbon Polymers. Four different fluorocarbons account for the bulk of the laboratory applications polytetrafluoroethylene, Teflon PTFE po-ly(chlorotrifluoroethylene), KEL-F tetrafluoroethylene-hexafluoropropylene copolymer, Teflon FEP and tetrafluoroethylene-perfluorovinyl ether copolymer, PFA. These polymers are inert with most chemicals and solvents at room temperature and exceptionally inert with oxidizing agents. They also have an exceptional resistance to temperature extremes. However, they are decomposed by liquid alkali metals, solutions of these metals in liquid ammonia, and carban-ion reagents such as butyllithium. Teflon retains some of its compliance at liquid hydrogen temperature. The maximum temperature which is recommended for continuous service is 260°C for Teflon PTFE and PFA, and about 200°C for Kel-F and Teflon FEP. 

Acetal translucent crystalline polymer is one of the stiffest TPs available. It provides excellent hardness and heat resistance, even in the presence of solvents and alkalies. Its low moisture sensitivity and good electrical properties permit direct competition with die-cast metal in a variety of applications. In addition, acetal has extremely high creep resistance and low permeability. Acetal is also available as a copolymer (Hoechst Celanese Corp. s Celcon) for improved processability. The homopolymer (DuPont s Delrin) has a very low coefficient of friction and its resistance to abrasion is second only to nylon 6/6. Acetals are frequently blended with fibers such as glass or fluorocarbon to enhance stiffness and friction properties. Acetal is not particularly weather-resistant, but grades are available with UV stabilizers for improved outdoor performance. Acetal, whether homopolymer or copolymer, is not used to any significant degree in forming structural foams. 

The thermal decomposition of salts of fluorinated acids gives tw o different types of products. depending on the reaction conditions and the type of cation. When the decarboxylation of alkali and alkaline earth metal salts is carried out in the presence of proton donors, such as water, alcohol, aniline, pyridine or other basic solvents, the product of the reaction is a fluorocarbon hydride. This is a general procedure for the preparation of 1 /Z-perfluoroalkanes. ... 

Peroxidic cure systems are applicable only to fluorocarbon elastomers with cure sites that can generate new stable bonds. Although peroxide-cured fluorocarbon elastomers have inferior heat resistance and compression set, compared with bisphenol cured types they develop excellent physical properties with little or no postcuring. Peroxide cured fluoroelastomers also provide superior resistance to steam, acids, and other aqueous solvents because they do not require metal oxide activators used in bisphenol cure systems. Their difficult processing was an obstacle to their wider use for years, but recent improvements in chemistry and polymerization are offering more opportunities for this class of elastomers [42]. 

SPE can be prepared by dissolving the polymer and an alkali metal salt in a mutual solvent and then evaporating the solution on a teflon fluorocarbon resin plate in a dry atmosphere. SPE films are obtained by casting the solution and heating at relatively low temperatures ( 150°C) under vacuum. The existence of a polymer/salt complex, however, is no guarantee that the material will be a good ionic conductor. 

The Ru-red or Ru-brown complex adsorbed in the Nafion membrane is probably present in a microheterogeneous environment imposed by hydro-phobic cluster made of fluorocarbon moiety and by hydrophilic cluster made of sulfonate ions, and the Ru-red or Ru-brown is electrostatically held by the sulfonate ions. In a polymer membrane, the metal complex molecules would be isolated and the microheterogeneous environment would alter the complex-solvent interaction. Such effects are well characterized for macromolecular metal complexes . Since Ru-red and Ru-brown water oxidation catalysts are strong oxidants in their higher oxidation states, they would attack organic ligands of the... 

Use Dry-cleaning solvent, vapor-degreasing solvent, drying agent for metals and certain other solids, vermifuge, heat-transfer medium, manufacture of fluorocarbons. 

Although the CFCs are not as stable as the fluorocarbons (FCs), they are unusually stable compounds. Dichlorodifluoromethane, CCI2F2 (CFC-12), is stable at 500°C in quartz. Trichloromonofluoromethane, CCI3F (CFC-11), begins to decompose at 450° C. The CFCs react with molten alkali metals and CCI2F2 reacts vigorously with molten aluminum, but with most metals they do not react below 200°C. An exception is the dechlorination of chlorofluorocarbons with two or more carbon atoms in the presence of Zn, Mg, or A1 in polar solvents. ... 

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