Reactions of cycloproparenes with metal carbenes

[figure: see text] Benzocyclopropene and cyclopropa[b]naphthalene react with dichloro-bis(tricyclohexylphosphine)methylideneruthenium, incorporating the metallacarbene to form unstable 3-ruthenacyclopentenes, which decompose to give o-xylylenes that can be trapped as Diels-Alder adducts by dimethyl acetylenedicarboxylate. In contrast, bis(eta 5-cyclopentadienyl)methylidenetitanium forms moderately stable 2- and 3-titanacyclopentene complexes.