Trimerisation of carbon suboxide at a di-titanium centre to form a pyrone ring system.

The reaction of the -bimetallic bis(pentalene)dititanium complex Ti(μ:η,η-Pn) (Pn = CH(1,4-SiPr)) with carbon suboxide (O[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]O, CO) results in trimerisation of the latter and formation of the structurally characterised complex [{Ti(μ:η,η-Pn)}{μ-CO}]. The trimeric bridging CO unit in the latter contains a 4-pyrone core, a key feature of both the hexamer and octamer of carbon suboxide which are formed in the body from trace amounts of CO and are, for example, potent inhibitors of Na/K-ATP-ase. The mechanism of this reaction has been studied in detail by DFT computational studies, which also suggest that the reaction proceeds the initial formation of a mono-adduct of with CO. Indeed, the carefully controlled reaction of with CO affords [Ti(μ:η,η-Pn) (η-CO)], as the first structurally authenticated complex of carbon suboxide.