摘要：

Ultrasonic irradiation of liquids produces acoustic cavitation: the rapid formation, growth, and implosive collapse of vapor filled vacuoles. This generates short-lived 'hot spots' with peak temperatures approx. 3000 K and nanosecond lifetimes. We have studied the effects of high intensity ultrasound on a variety of metal carbonyls and have observed the general phenomenon of sonochemical ligand dissociation, which often produces multiple CO substitution. Fe(CO)//5, for example, upon sonolysis, yields Fe//3(CO)//1//2 in the absence of additional ligands and Fe(CO)//3L//2 and Fe(CO)//4L (L equals phosphine or phosphite) in their presence. Similar substitution patterns are observed for Fe//3(CO)//1//2, Mn//2(CO)//1//0, Cr(CO)//6, Mo(CO)//6, and W(CO)//6. In all cases examined the rates of sonochemical ligand substitution are first order in metal carbonyl concentration and independent of L concentration. In addition, ln K//o//b//s//d correlates well with solvent system vapor pressure. These results are consistent with a dissociative mechanism in which coordinatively unsaturated species are produced by the cavitation process. Further use of these transient intermediates is made as alkene isomerization catalysts. Sonocatalysis by a wide range of metal carbonyls shows many similarities to photocatalysis, but with different relative efficiencies and selectivities also observed.

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