NMR-Spektroskopie an paramagnetischen Komplexen, XIX 13C-und 1H-NMR-Zugang zu gewinkelten Titanocenen/NMR Spectroscopy on Paramagnetic Complexes, XIX 13C and 1H NMR Access to Bent Titanocenes

Abstract

Abstract From [(RC5H4)2TiCl]2, R = H (1), CH3 (2) and C2H5 (3), (C5H5)2TiBH4 (4) and (C5H5)2Ti(CH3CN)Cl (5) the first paramagnetic 13C and 1H NMR spectra in the series of bent titanocenes have been obtained. Broad signals shifted to low field originate from the cyclopentadienyl protons while the corresponding 13C signals appear at high field relative to a diamagnetic reference. This is ascribed to π-polarisation which dominates the transfer of unpaired electrons onto the five-membered ring while σ-polarisation delocalizes them onto other ligands. The NMR shifts indicate that titanocene halides are antiferromagnetically coupled in solution, the extent depending on the solvent and on five-membered ring substituents. In the gas phase only monomers are found by mass spectroscopy. Paramagnetic NMR further reveals proton exchange in 4 and ligand dissociation in 5.