An experimental electron density study on "1-zirconacyclopent-3-yne".

An electron density analysis of the 1-zirconacyclopent-3-yne complex has been carried out based on X-ray diffraction data, showing that the coordination mode of the but-2-yne-1,4-diyl ligand to the metal is a resonance hybrid between eta2-sigma, sigma-coordination, as the major contributor, and eta4-pi, pi-coordination.