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.

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.6837297