Cp2Fe2(CO)4is apparently different from the other metal-metal-bonded carbonyl dimers in that irradiation of this dimer in the presence of ligands does not lead to disproportionation: Cp2Fe2(CO)4+ L + hv → CpFe(CO)2“ + CpFe(CO)3_„Ln+. However, it was demonstrated that with most ligands the disproportionation reaction does occur but the back-reaction of the products is facile. The back-reaction can be prevented by reacting further one of the products. For example, in CH2C12solution, CpFe(CO)2“ reacts with the solvent to give CpFe(CO)2CH2Cl and the back-reaction is prevented. The mechanism of the disproportionation reaction is proposed to be a chain mechanism involving 19-electron adducts formed by the reaction of a 17-electron metal radical with a ligand, e.g. CpFe(CO)2+ L → CpFe(CO)2L. It is demonstrated that the 19-electron adducts are powerful reductants. The following organometallic, organic, and inorganic substrates were reduced by the 19-electron species, thereby demonstrating the versatility of these species as reducing agents: CpMo(CO)3Cl, Fe(CN)63“, Mn2(CO)10, Re2(CO)10, Ru3(CO)12, Fe(CO)5, N-n-butylpyridinium, and Cp2Co+. Experiments involving the reduction of Cp2Co+demonstrated several mechanistic points concerning the reactivity of 19-electron species.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry