A new route to complexes containing the tetracarbon (C4) ligand

Pyrolysis of a solution of (Ru3(CO)11}2(mu-bdpp) (bdpp = bis(diphenylphosphino)butadiyne) yielded the complex (RU3(mu-PPb2)-(CO)9}2(mu6-C4), which contains a mu6-C4 ligand symmetrically bridging two RU3(mu-PPh2)(CO)9 clusters. When the complex {Fe(CO)4}2-(mu-bdpp) was heated in the presence of Fe2(CO)9 another example of a C4 complex, {Fe2(mu-PPh2)(CO)6}2(mu-C4), was obtained. Both complexes were characterised by X-ray structure determinations; the C4 ligand behaves as a buta-1,3-diyne-1,4-diyl system.