PREPARATION AND PROPERTIES OF (S,S)-[TI((R,R)-CYCLACENE)CL2], A CHIRAL STRAPPED BENT METALLOCENE

The ligand (1R,2R)-trans-1,2-bis(1-indenylmethyl)cyclopentane has been prepared, and its dilithio salt was allowed to react with TiCl4.2THF; after reduction of this product, the complex (S,S)-[Ti((R,R)-cyclacene)Cl2] was isolated. The trans-1,2-dimethylenecyclopentane group joining the two groups induces the formation of one chiral diastereomer. The crystal structure shows that the two tetrahydroindenyl groups are not symmetrically disposed although the H-1 NMR spectrum at various temperatures indicates a symmetric structure, at least on an NMR time scale. Circular dichroism spectra are recorded for the complex. The possible origins of the unsymmetrical structure are discussed in terms of the strap size.