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), 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.