Etude de divers types de diastereotopie par RMN de 1H et de 13C dans les series du ferrocene et du titanocene

Abstract

The influence of a chiral group on the 1H and 13C NMR parameters of ferrocenes and titanocenes is studied. The difference of screening due to the diastereotopy of the cyclopentadienyl carbon nuclei is usually larger than the non-equivalence of corresponding proton chemical shifts. If the chiral group is the titanium atom itself a diastereotopy is also introduced into the cyclopentadienyl ring. Proton spectra obtained at 250 MHz, INDOR and off-resonance experiments, using chemical shift reagents permit a complete analysis of the proton and carbon spectra of some derivatives, especially ferrocene with a CH(CH 3)(CH 2CO bridge and titanocene with a CH(CH 3)CH 2CH 2 bridge. The result give information on the stereochemistry, and preferred conformations are identified.