The crystal structure of π-cyclopentadienylbis(acetylacetonato)chlorozirconium(IV), π-C5H5(C6H7O2)2-ZrCl, which crystallizes with the symmetry of the monoclinic space group P21/c, has been determined by equiinclina-tion Weissenberg single-crystal X-ray diffraction techniques. The theoretical density (1.553 g cm-3) calculated for four molecules per unit cell with the observed lattice parameters (α = 8.42 ± 0.01, b = 15.66 ± 0.01, c = 15.17 ± 0.02 Å, β = 123° 25ʹ ± 4ʹ) is in agreement with the measured value (1.556 ± 0.005 g cm-3). The final discrepancy factor, R = 0.092, results from a full-matrix least-squares refinement of visually estimated relative intensities for 1453 reflections (sin ϴ/θ < 0.54 [formula-omitted], Cu Kα radiation). The observed dodecahedral stereochemical configuration of the molecule is compatible with π bonding between the cyclopentadienyl ligand and the zirconium atom and also appears to allow dπ-pπ, interaction between B oxygen and the zirconium atoms. Intermolecular forces within the lattice, which exhibits distinct layers, appear to be confined to van der Waal's interactions. © 1969, American Chemical Society. All rights reserved.