Sonochemical ligand substitution

Sonochemical ligand substitution readily occurs with a variety of other metal carbonyls, as shown in Table IV. In all cases, multiple ligand substitution originates directly from the parent carbonyl. The rates of sonochemical ligand substitution of the various metal carbonyls follow their relative volatilities, as predicted from the nature of the cavitational collapse. 

In the presence of added Lewis bases, sonochemical ligand substitution also occurs for Fe(C0)5, ancl act or roost metal carbonyls. Sonication of Fe(C0)5 in the presence of phosphines or phosphites produces Fe(C0)5 nLn, n=1, 2, and 3. The ratio of these products is independent of length of sonication the multiply substituted products increase with increasing initial [L] Fe(C0)i L is not sonochemically converted to Fe(C0)3L2 on the time scale of its production from Fe(C0)5. These observations are consistent with the same primary sonochemical event responsible for clusterification ... 

The transient nature of the cavitation event precludes conventional measurement of the conditions generated during bubble collapse. Chemical reactions themselves, however, can be used to probe reaction conditions. The effective temperature realized by the collapse of clouds of cavitating bubbles can be determined by the use of competing unimolecular reactions whose rate dependencies on temperature have already been measured. The sonochemical ligand substitutions of volatile metal carbonyls were used as... 

The sonolysis of Mn2(CO)10 makes for an interesting comparison (186), since either metal-metal (as in photolysis) (187) or metal-carbon (as in moderate temperature thermolysis) (188) bond breakage could occur. Ligand substitution will occur from either route producing the axially di-substituted Mn2(CO)8L2. Using benzyl chloride as a trap for the possible intermediacy of Mn(CO)5, the sonochemical substitution of Mn2(CO)10 has been shown to follow the thermal, rather than the photochemical, pathway of dissociative CO loss. 

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