NMR-Spektroskopie an paramagnetischen Komplexen, XXVII [1] Paramagnetische 1,1' .2,2' .3,3' .4,4' -Oktamethylmetallocene / NMR Spectroscopy on Paramagnetic Complexes, XXVII [1] Paramagnetic 1,1' .2,2' .3,3' .4,4' Octamethylmetallocenes

Abstract

Abstract The tetramethylated cyclopentadienyl anion has been prepared from tiglinic acid and reacted with solvated metal(II) chlorides to give new octamethylmetallocenes (Me-jcp^M. For M = V, Cr, Co and Ni the paramagnetic 1H and 13C spectra have been recorded. The NMR data prove the molecular structure and show that all methyl groups rotate almost freely. The methyl proton resonance of the nickelocene may serve as a probe for the adjustment of metallocene properties by ring substitution. Based on qualitative MO arguments the correlation of electron spin densities and paramagnetic shifts lead to an understanding of the signal splitting of cobaltocenes. From the electronic point of view the octamethylmetallocenes may be regarded as being in vers to 1,1'-dimethylmetallocenes