Silicon‐Bridged Homocyclopentadienides: Metal‐Assisted Facile Ring Expansion of Cyclopentadienide by Transient Imino(Metallophosphino)Silylenes

In this study, we report the aromatic C─C bond cleavage of cyclopentadienide by transient imino(metallophosphino)silylenes through the reaction of silylene equivalents with CpCo(CO) 2 , enabling the transformation of cyclopentadienides into silicon‐bridged homocyclopentadienides. The presence of homoaromaticity in these species is substantiated by NICS and ACID analyses. Experimental observations, in conjunction with detailed quantum chemical calculations, support a mechanistic scenario that metal‐assisted, silylene‐mediated cyclopentadienide activation proceeds via a formally Büchner ring‐expansion pathway.