Mechanism of the Generation of Ketenimine−M(CO)n Complexes (M = Cr, W, Fe) from Fischer Carbenes and Isocyanides

The mechanism of the thermal formation of ketenimine complexes through the reaction of group 6 (chromium and tungsten) and 8 (iron) Fischer carbenes and isocyanides has been studied computationally within the density functional theory framework. The computational data have been compared to the reported experimental results. It is found that the insertion of the N⋮C bond of the isocyanide into the MC bond of the Fischer carbene complexes, which leads to N-metalated-ketenimine complexes, occurs via metallacyclopropanimine species, rather than the proposed ylide complexes, followed by isomerization and 1,2-metallotropic rearrangement. We also studied the 6π-electrocyclization process of dienyl−ketenimine complexes, which leads to o-alkoxy aniline compounds. In terms of the synchronicity, activation energy, and aromaticity, the effect of the metal in this electrocyclization transformation is almost negligible.