An Improved Protocol for the Synthesis of [(η4-C4R4)Co(η5-C5H5)] Complexes

International audience; The reaction of bulky alkynes C2R2 with (η5-C5H5)Co(CO)(dimethyl fumarate) under microwave irradiation provides complexes of the type [(η4-C4R4)Co(η5-C5H5)] in good to excellent yields. This protocol represents a significant improvement over those reported previously. In particular, the formation of insertion products such as cyclopentadienones or cyclohexadienes can be avoided. In addition, because of the exceptional stability of (η5-C5H5)Co(CO)(dimethyl fumarate), the reactions can be carried out in crude solvents. The easy access to [(η4-C4R4)Co(η5-C5H5)] complexes stimulated a study of their reactivity, notably under cross-coupling conditions.