Synthesis and Structure of Seven‐Membered Metallacycloalkynes (Eur. J. Inorg. Chem. 3/2013)

Seven‐membered metallacycloalkyne compounds were synthesized. The reaction of the zirconocene–ethylene complex and ( Z )‐1,4‐bis(trimethylsilyl)buta‐1,2,3‐triene gave a mixture of 1‐zirconacyclopent‐3‐yne and 1‐zirconacyclohept‐3‐yne. In contrast, zirconocene–alkyne complexes, such as those of 1‐(trimethylsilyl)prop‐1‐yne and diphenylacetylene, gave 1‐zirconacyclohept‐2‐en‐5‐yne in good yields. Consideration of structural parameters suggests that both a seven‐membered cyclic alkyne and a five‐membered structure contribute to generation of this complex. Coupling of benzyne and [3]cumulenes on a metal was also found to afford the corresponding metallacycles.