Tungsten-induced reactions

Since the specific activity of a radionuclide produced by particle-induced reactions is a direct function of the incident particle flux, an increase in the incident particle flux results in an absolute increase in the specific activity of the product This relationship is linear for simple reactions and nonlinear for complex reactions. It is important to note that the half-lives, production and depletion cross sections, and irradiation time are equally important. Several important radionuclides have long physical half-lives and low production cross sections requiring long irradiation periods even in the highest neutron flux available. An example in this category is tungsten-188 (half-life 69 days parent for rhenium-188). 

Lutetium-177 produced by neutron capture reactions Iodine-125 produced by neutron capture followed by Tungsten-188 produced by double neutron capture Tin-117m produced by neutron inelastic scattering Copper-67 produced by fast neutron-induced reactions... 

SRN I reactions are generally accelerated by irradiation with tungsten lamps (200-500 W) or fluorescent lamps. They are retarded in the presence of oxygen or other radical inhibitors. Recently, microwave irradiation has been shown to be effective in inducing S l reactions the reaction of Eq. 5.37 proceeds under microwave irradiation (900 W, 5 min) in the presence of trace amounts of water.55... 

Tungsten has been used to induce complete combustions, for example, in the studies ofWTe2 [123],Mo5Si3 [125],andSi3N4 [126], In these cases, the sample was typically arranged as shown in figure 7.12. The compound under study (G), with the sulfur fuse sprinkled on top was placed in a thin tungsten saucer (I), supported by a nickel crucible (H) with holes in the sides (K) to allow rapid circulation of the fluorine around the combustible materials as the reaction proceeded. 

Some examples have been reported of tethered r 6-arene complexes of molyb-denum(II) and tungsten(II) that incorporate oxygen as the auxiliary donor atom.37 40 Reaction of neat 2,6-diphenylphenol with [MH4(PMePh2)4] (M = Mo, W) at 150 °C gives the tethered hydrido(aryloxo)metal(II) complexes 30 and 31.36 A metal-hydride bond is probably first cleaved by the phenolic oxygen with loss of H2 coordination of the pendant arene then induces loss of another equivalent of H2. 

Fp C=CC2[Co2(CO)6]-moieties linked by a C-C single bond and is obtained from the reaction of the tetrayndiyl complex Fp i-(C=C)4 and Co2(CO)8.422 The two C2Co2 cores, which again involve the inner C=C triple bonds, induce a transoid conformation (S-shaped) in the carbon chain, analogous to that described above for the tungsten complexes. 

The coupling reaction of (cyclopropylcarbinyl)WCp(CO)2 and the carbonyl ligand, induced by trimethylphosphine (see Section II.D) gave initially an >/ -ketenyl complex, which under CO pressure (60 bar) adds a further carbonyl ligand to give a pentacoordi-nated f/ -cyclopropylketenyl tungsten complex (equation 132) . This unusual cyclo-... 

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