Tungsten, ethane

Tris(aminomethyl)ethane, 2044 1,1, l-Tris(bromomethyl)methane, 1550 Tris(cyclopentadienyl)cerium, 3683 Tris(hydroxymethyl)methylamine, 1731 Tungsten hexamethoxide, 2604... 

B. TRICARBONYL-1,2-BIS(DIPHENYLPHOSPHINO)ETHANE (FULLERENE-60)TUNGSTEN(0), W(CO)3(dppe)C6o... 

C30H24O4P2W, Tungsten(O), tetracarbonyl 1,2-bis(diphenylphosphino)ethane -, 34 108 C32Hi2BF24Na, Borate, tetrakis(3,5-bis(trifluoro-methyl)phenyl)-, sodium salt, 34 5 C32H29FeNP2, Iron(II), cyano( ) -cyclopentadie-nyl)-l,2-bis(diphenylphosphino)ethane-, 34 161... 

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

C89H24O3P2W, Tungsten(O), tricarbonyl 1,2-bis(diphenylphosphino)ethane -(fullerene-60)-, 34 109... 

POgOsgCgsHis, Osmium, octacarbonyl-(triphenylphosphiue)-(/i3-7) 7) 7j -fullereue-60)tri-, 34 227 P2C26H24, 1,2-Bis(dipheuylphosphino)ethane, dppe, complexes with tungsten(O),... 

Further evidence that the type of exchange of propane depends on the nature of the catalyst was obtained by Kemball 18). Films of tungsten gave distributions of products similar to those obtained with ethane over this metal and the course of the reaction followed Equation (5). This in-... 

CjHjS, Thiophene, tetrahydro-gold complexes, 26 85-87 C4H,NO, 2-Propenamide, 2-methyl-nickel complex, 26 205 C4H1()02, Ethane, 1,2-dimethoxy-solvates of chromium, molybdenum, and tungsten carbonyl cyclopentadienyl complexes, 6 343 tungsten complex, 26 50 ytterbium complex, 26 22 C4H i02.NaC5H5, Ethane, 1,2-dimethoxy-compd. with cyclopentadienylsodium, 26 341... 

He concludes that the first (associative) mechanism gives values nearest the observed heat of adsorption determined by Beeck (30), and is therefore accepted as nearest the truth (34) (Qo (calculated) = 42 kcal./ mole Qo (observed) = 58 kcal./mole). Experiments on tungsten and nickel films (Beeck (35), Trapnell (36), and more recent work in Rideal s laboratory) have shown that when ethylene is added to a clean metal surface ethane appears in the gas phase. A self hydrogenation mechanism must be operative and at least in these cases dissociation of ethylene must occur on the catalyst. It is suggested that the calculations might be complicated by the energy of bond strain in the adsorption of an ethylene molecule to the fixed lattice distances of the metal. 

Each of the various processes of adsorption may have desorptions of the reverse forms, for example, dissociative adsorption may have as its reverse, associative desorption. However, the process of chemisorption may not be reversible [ 1.2.2(c)]. Desorption may lead to species other than that adsorbed, for example, ethane dissociatively adsorbed on clean nickel gives little or no ethane upon desorption, 1-butene dissociatively adsorbed to methylallyl and H on zinc oxide gives mainly 2-butenes upon desorption, and some W03 may evaporate from tungsten covered with adsorbed oxygen. 

A tungsten sulfide catalyst which had been inactivated by extended operation had, as expected, a considerably lower adsorption capacity than new catalyst. This is shown in Fig. 3 for the adsorption of ethane at 100°C. The adsorption rate of gases on used, inactive WS2 catalyst seems to be decreased to an even greater extent. 

The group 5-7 supported transition metal oxides (of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and rhenium) are characterized by terminal oxo bonds (M =0) and bridging oxygen atoms binding the supported oxide to the cation of the support (M -0-MSUpport). The TOF values for ODH of butane or ethane on supported vanadia were found to depend strongly on the specific oxide support, varying by a factor of ca. 50 (titania > ceria > zirconia > niobia > alumina > silica). 

Tetrachlorobis(triphenylphosphine)tungsten(IV) (4.5 g, 53 mmole) and 1,2-bis-(diphenylphosphino)ethane (2.1 g, 5.3 mmole) are heated in toluene (50 mL, distilled from sodium) at 70° for 3 hours in a 100-mL flask carrying a reflux condenser. The resulting yellow-green solid is filtered using a Schlenk filter, washed with toluene (30 mL) and diethyl ether (30 mL), and dried (10 2 torr, 20°). Yield 2.4 g, 89% it is sufficiently pure for subsequent preparations. Anal. Calcd. for C26H24C14P2W C, 43.1 H, 3.3. Found C, 44.5 H, 3.6. 

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