Crystal and molecular structures of difluorobis-(π-cyclopentadienyl)zirconium(IV) and di-iodobis-(π-cyclopentadienyl)zirconium(IV)

Abstract

The crystal and molecular structures of the compounds (π-C₅H₅)₂ZrF₂ and (π-C₅H₅)₂Zrl₂, have been elucidated by X-ray diffraction studies. The I–Zr–I and (π-C₅H₅)–Zr–(π-C₅H₅) angles in the di-iodide are 96·2 and 126·3°, and the F–Zr–F and (π-C₅H₅)–Zr–(π-C₅H₅) angles in the difluoride are 96·2 and 127·8°. The mean zirconium–carbon distance in the di-iodide, 2·48 Å, does not differ significantly from that in the difluoride, 2·50 Å. The zirconium–iodine and zirconium–fluorine distances, 2·85 and 1·98 Å, differ by 0·87 Å, whereas the covalent radii of iodine and fluorine atoms differ by 0·69 Å. Crystals of (π-C₅H₅)₂ZrF₂ are orthorhombic, of space group F2mm, with a= 6·076, b= 10·475, c= 14·848 Å, and Z= 4; the X-ray intensities were measured by means of a computer-controlled four-circle diffractometer employing Mo-K_α radiation, and least-squares refinement of the atomic co-ordinates and thermal parameters resulted in convergence at R 3·0% for 373 independent reflections. Crystals of (π-C₅H₅)₂Zrl₂ are monoclinic, of space group C2/c, with a= 14·20, b= 7·25, c= 13·53 Å, β= 117·1°, and Z= 4; photographic intensity data obtained with Mo-K_α radiation were estimated visually, and least-squares refinement of the atomic parameters was completed at R 5·7% for 749 independent reflections.