To conclude, the trends observed are consistent with the mechanistic model proposed in Scheme 3, where the Lewis base may either be the solvent, or the substrate, and where the disproportionation of the [Co2(CO)8] is a key step for the generation of an active species: no carbonylation activity is observed in the conditions where the disproportionation of the precursor [Co2(CO)8] is less favoured, i.e., in a noncoordinating solvent, and at high CO pressure (see Table , entries 3 and 6).