Photochemistry of osmocene. Reductive elimination and generation of elemental osmium

Osmocene is intrinsically photoactive. It photolyzes in n-hexane by a reductive elimination leading to the generation of metallic osmium. Moreover, both cyclopentadienyl anions as ligands in osmocene are oxidatively eliminated. Surprisingly, they are liberated as benzene and cyclobutadiene which is trapped by diphenyl acetylene. As a result of this trapping o-terphenyl is formed. It is suggested that in the LF excited state both cyclopentadienyl ligands undergo a bending in agreement with the previous conclusions. The close approach of both ligands facilitates a CH group transfer between them. The subsequent decay generates elemental osmium, benzene and cyclobutadiene as photolysis products.