Tungsten complexes dihydrogen

As an experimental example of such an INS lineshape analysis, the INS spectra of the protonated isotopomer of the same tungsten dihydrogen complex W(PCy3)(CO)3( /2-H2) are presented. 

Hoff has shown that the rate of dissociation of a tungsten-dihydrogen complex is at least one order of magnitude faster than the rate of oxidative addition (H-H bond cleavage) to a dihydride complex [128]. 

The first known r -dihydrogen complexes, so-called non-classical hydrido complexes, were the molybdenum and tungsten compounds, M(CO)3(PR3)2(ti -H2) (M = Mo, W R = /-Pr) isolated for the first time by Kubas [35]. In order for the... 

MoH(ti5-C5H5)(CO)2(PCy3)] was more active (2 tumovers/h). Similar but water soluble tungsten and molybdenum complexes are known [223-226] which would allow the use of water as solvent for such reactions. It is noteworthy, though, that ionic hydrogenation of ketones by dihydrogen complexes has so far been observed only in non-aqueous solutions [223,227] perhaps the coordination of a ketone is disfavoured in water due to competition by H20. 

We also employed other ruthenium dihydrogen complexes for the protonation of the coordinated dinitrogen in complex (2b). Typical results are shown in Table 3 [21]. Ammonia is formed in higher yields (up to 79% based on tungsten) when dinitrogen complex (2b) is similarly treated with tra s-[RuCl(r -H2)(dppe)2]X... 

Evidence for tungsten dihydride complexes was obtained directly, as discussed above, but analogous complexes of molybdenum have not been directly observed. Indirect evidence for molybdenum dihydrides (or dihydrogen complexes) comes from the reaction shown in Equation 3.21, in which the molybdenum ketone complex heterolytically cleaves H2 in the reaction with a hindered base. 

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