Metal carbonyl species CpFe

Flash photolysis has now been applied to a wide range of metal carbonyl species in solution, including Mn2(CO)10 (37), [CpFe(CO)2]2 (38), and [CpMo(CO)3]2 (39). In almost every case, interesting data have emerged, but, as with Cr(CO)5, the structural information is usually minimal. Thus, the radical Mn(CO)5 has been generated in solution by flash photolysis (37), the rate constant for its bimolecular recombination has been measured, but the experiments did not show whether it had Z>3h or Qv symmetry. Some experiments have been unsuccessful. Although the fragment Fe(CO)4 is well known in matrices (15), it has never been... 

CpFe(CO)2 Na and after treatment with acid and decomplexation with sodium iodide in acetone the free alkene is isolated (Scheme 97). In addition, certain metal carbonyls like Co2(CO)g, Fe(CO)s and Mo(CO)e effectively deoxygenate epoxy-esters and -ketones. Also low-valent tungsten species and metallocenes may be used for the regeneration of alkenes. 

The methyl transfer reactions are envisoned as arising from SN2 displacement of a less nucleophilic metal carbonyl anion by a more nucleophilic carbonyl anion. CpFe(CO)2 is the more basic species (69) and therefore abstracts methyl from the less basic CpMo(Me)(CO)3. CpMo(CO)3 and Mn(CO)5 are bases of comparable strength, and, therefore, the reaction either of MnMe(CO)s with CpMo(CO)3" or of CpMo(Me)(CO)3 with Mn(CO)5 gave mixtures of CpMo(Me)(CO)3 and Mn(Me)(CO)s. 

Indeed, organometallic precatalysts can be transformed during an induction period into catalyticaUy active species that do not contain metal-carbon bonds. For example, molybdenum [7a] and tungsten [7b] carbonyls catalyze aerobic photooxygenation of cyclohexane to cyclohexyl hydroperoxide (primary product) and cyclohexanol and cyclohexanone (Fig. 1.4). The proposed mechanism is shown in Fig. 1.5. It includes the formation during the induction period of an oxo derivative. Complexes CpFe( r-PhH)BF4 and ( 7r-durene)2Fe(BF4)2 also catalyzed the aerobic alkane photooxygenation [7c]. The mechanism has not been studied. 

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