Nuclear recoil reactions in organomanganese compounds. III. Mn(CO)5

Abstract

Experimental evidence is presented which shows that upon neutron irradiation of the compounds Mn2(CO)10, CpMn(CO)3, and CH3CpMn(CO)3 the recoiling 56Mn atom gathers carbonyl radicals to stabilize itself in the group Mn(CO)5, with about 10% radiochemical yield. Basically, the experiments involved addition of iodine to the irradiated compound and identification of the radioactive IMn(CO)5 by carrier techniques. It is suggested that in Mn2(CO)10 targets, the species produced is the •Mn(CO)5 radical itself. Some experimental data are given to show that this radical is stable for over 1 h in the solid at room temperature, but decomposes rapidly above about 60°. The radical decomposes in 20–30 s in solution. In both other target compounds, the species produced is chemically more stable, although it reacts rapidly with iodine. This species is found to be HMn(CO)5, which occurs to the extent of 10–12% in CpMn(CO)3. CH3Mn(CO)5 was also detected in CH3CpMn(CO)3 targets, and its yield was found to be a function of the concentration of isooctane used as diluent in the targets.Results from other studies are discussed in the light of the present data, and it is concluded that in general, in neutron-irradiated metal carbonyl compounds, the recoil atom is able to accumulate carbonyl radicals to a greater extent than is consistent with the composition of the target compound.