Trimerisation of carbon suboxide at a di-titanium centre to form a pyrone ring system
Bis(pentalene)dititanium Ti2(μ:η5,η5-Pn†)2 trimerises carbon suboxide (OCCCO) to form [{Ti2(μ:η5,η5-Pn†)2}{μ-C9O6}], which contains a 4-pyrone core, via the monoadduct [Ti2(μ:η5,η5-Pn†)2 (η2-C3O2)].