The Ferromagnetic Coupling Mechanism in Hetallocenium/π-Anion Stacks as seen by NMR Spectroscopy

Abstract

Abstract The 1H and 13C NMR spectra of selected nickelo-cenium, chromocenium, and ferrocenium ions are reported. The sign of the signal shifts establishes positive or negative electron spin on the ligand for Ni or Cr sandwiches, respectively. Hyperconjugative spin transfer to β carbon atoms of substituted ferrocenium ions is used to prove negative spin on their ligands. For (Cp *)Cr(arene) derivatives negative spin on the ligand is indicated by characteristic shifts of the β-proton signals. The results meet the requirements of the mechanism of Kahn and Kollmar 5b c for magnetic intra-stack interactions.