What do titano- and zirconocenes do with diynes and polyynes?

A thorough investigation of the reactions of diynes, R(C=C)(2)R, and polyynes, R(C=C),R, with titanocene and zirconocene was performed using the metallocene sources Cp2M(C)(eta(2)-Me3SiC=CSiMe3) (M = Ti, L = -; M = Zr, L = THF, pyridine). The conversions show an array of different products generated in complexation, coupling, and cleavage reactions. These results include remarkable structures (e.g., five-membered metallacyclocumulenes) and reactions (e.g., C-C single-bond cleavage). In addition, the first C-C single-bond metathesis in homogeneous solution was discovered. The presented findings have been supported by theoretical studies.