Cp2ZrCH(SiMe3)CCCH(SiMe3):: A five-membered 1-zirconacyclopent-3-yne?

Density functional theory calculations at the B3LYP level were performed to study the electronic structure of a recently synthesized zirconocene complex, Cp2ZrCHRCCCHR (R = SiMe3). Through detailed bonding analyses and stability studies, we conclude that the originally proposed metallacyclopentyne form cannot adequately describe the complex. Instead, a resonance hybrid between a cumulene complex form and a metallacyclopentyne Lewis structure is required to account for the structure and stability of the complex.