SYNTHESIS AND CRYSTAL-STRUCTURE OF 1,1'-(3-OXAPENTAMETHYLENE)-BRIDGEDBIS(INDENYL) ANSA-LANTHANOCENE CHLORIDES

Several representative chiral ansa-lanthanocene chlorides have been sy nthesized and characterised with a rac:meso ratio of 6:1 using an ethe r-bridged bis(indenyl) ligand. The structure of these complexes was id entified by X-ray crystallography in the solid state or H-1 NMR spectr oscopy in solution. The ligand proved to be rather rigid leading to th e favoured unsymmetric rac isomer. The H-1 NMR spectra indicated that the configuration of the rac isomer in solution agrees well with that in the solid state and, interestingly, the two bridged indenyl rings o f the rac isomers slowly oscillated.