ansa-Metallocene derivatives : Molecular structure and proton magnetic resonance spectra or methylene- and ethylene-bridged dicyclopentadienyltitanium compounds

Abstract

The molecular structure of the methylene-bridged titanocene dichloride, CH2(C5H4)2TiCl2, and that of the novel, ethylene-bridged derivative, (CH2)2-(C5H4)2TiCl2 have been determined by X-ray diffraction methods. In these molecules the cyclopentadienyl ligands are highly restricted in their torsional mobility. An angle of 65° between the two ring planes, a C-C-C angle of 97.5° at the methylene carbon atom, and other geometrical data, indicate a high degree of strain in the methylene-bridged derivative, whereas the ligand geometry of the ethylene-bridged derivative does not deviate significantly from that of unbridged titanocene dichloride. 1H NMR spectra for ansa-titanocene derivatives of general type (CH2)n-C5H4)2TiX2 (n = 1–3, X = Cl, CH3, CO) are reported; the varying degrees of splitting between the high-field and the low-field portions of an A2B2 resonance pattern due to the cyclopentadienyl hydrogen atoms are interpreted in terms of bonding goemetries.