Benzene-, tungsten

Bis(benzamidinate)zirconium catalysts, for stereoselective propylene polymerization, 11, 708 Bis(r -benzene)tungsten, as metal vapor synthesis milestone, 1, 236... 

Development of +ve hearth electron-beam furnace bis( 7-benzene)tungsten (1978) ... 

Using an electron-gun source, tungsten atoms were reacted with benzene, toluene, or mesitylene at 77 K, to form the expected (arene)2W complex (42) in a yield of 30%, compared with the —2% yield from the previously published, bis(benzene)W synthesis (32). These arene complexes are reversibly protonated, to give the appropriate [(T7-arene)2WH] species. By using the same technique, the analogous, niobium complexes were isolated (43). 

Field electron emission coupled with flash-filament studies have been employed by Condon and Hansen to study benzene chemisorption on tungsten (21). Evidence was obtained for the chemisorption of benzene by a single bond (probably of -character) to the surface. This form of asso-ciatively adsorbed benzene [(I), Scheme 1] appeared to exist in equilibrium with cr-adsorbed-CeHs (II) and adsorbed atomic hydrogen. 

Anderson and Kemball (35) examined the reaction between gaseous deuterium and benzene catalyzed by evaporated films of iron, nickel, palladium, silver, tungsten, and platinum. The order of reactivity (estimated from the temperature at which the addition reaction achieved an initial rate of 1% per minute for a 10 mg film at certain specified reactant... 

Reaction of unsaturated chromium and tungsten carbene complexes 407 with piperidazine provides amino-carbene complexes 408 and 409. Although various solvents such as CH2C12 benzene, ether, and THF can be used in the reaction, the yields of the desired products 410 are 32-59%, and considerable amounts of by-products 409 are formed. The carbene complexes 408 are rather stable and can be stored in a refrigerator. Oxidation of both complexes with iodoso-benzene affords oxo derivative 410 in 70% (M = Cr) and 41% (M =W) yields (Scheme 64) <1994CL777>. 

Lewis Bases. A variety of other ligands have been studied, but with only a few of the transition metals. There is still a lot of room for scoping work in this direction. Other reactant systems reported are ammoni a(2e), methanol (3h), and hydrogen sulfide(3b) with iron, and benzene with tungsten (Tf) and plati num(3a). In a qualitative sense all of these reactions appear to occur at, or near gas kinetic rates without distinct size selectivity. The ammonia chemisorbs on each collision with no size selective behavior. These complexes have lower ionization potential indicative of the donor type ligands. Saturation studies have indicated a variety of absorption sites on a single size cluster(51). 

Figure 7 Reaction of tungsten atoms with cyclopentane, (i and iv) Co-condensation at -196 °C (ii) Cyclopenta-diene in benzene at 60 °C and (iii) Dihydrogen at 50 atm.

Hydrotreating also produces some residuals in the form of spent catalyst fines, usually consisting of aluminum silicate and some metals (e.g., cobalt, molybdenum, nickel, tungsten). Spent hydrotreating catalyst is now listed as a hazardous waste (K171) (except for most support material). Hazardous constituents of this waste include benzene and arsenia (arsenic oxide, AS2O3). The support material for these catalysts is usually an inert ceramic (e.g., alumina, AI2O3). 

Telluroesters (acyl tellurides) have been recognized as excellent sources of acyl radicals upon photolysis with a 250 W tungsten lamp, or thermal process (benzene at reflux) in the... 

Pentacarbonyl(a-methoxybenzylidene)tungsten(0)7 (0.89 g, 2.0 mmole) and a magnetic stirring bar are placed in a flame-dried, 100-mL, round-bottomed flask fitted with a rubber septum. The flask is flushed with nitrogen, 50 mL of diethyl ether (freshly distilled from sodium and benzophenone) is added, and the resulting red solution is cooled to -78°. A double-titrated8 solution of phenyllithium in 70 30 benzene/diethyl ether (1.25 mL, 1.85 M, 2.31 mmole, 2.10 M total base, 2.63 mmole) is added by syringe to the well-stirred solution. The anionic intermediate formed is thermally unstable at room temperature and is kept at -78° (Dry Ice-acetone) to avoid decomposition. 

C68FI56N4P4W, Tungsten(O), bis(l,4-diisocyano-benzene)bis(l,2-bis(diphenylphosphino)-ethane)-, 34 28... 

CsHuN, Ethanamine, A-ethyl-A-methyl-tungsten complex, 26 40, 42 C6HF5, Benzene, pentafluoro-gold complexes, 26 86-90 C H4I2, Benzene, 1,2-diido-iridium complex, 26 125 CJT, Phenyl platinum complex, 26 136 C,H,N, Pyridine osmium complex, 26 291 OHtS, Benzenethiol osmium complex, 26 304 QH7P, Phosphine, phenyl-cobalt-iron complex, 26 353 QH 1-Butyne, 3,3-dimethyl-mercury-molybdenum-ruthenium complex, 26 329-335 C6H 4P, Phosphine, triethyl-platinum complex, 26 126 platinum complexes, 26 135-140 CsHisPO, Triethyl phosphite iron complex, 26 61... 

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