Giant Residual Dipolar 13C–1H Couplings in High‐Spin Organoiron Complexes: Elucidation of Their Structures in Solution by 13C NMR Spectroscopy

High‐spin Fe^II–alkyl complexes with bis(pyridylimino)isoindolato ligands were synthesized and their paramagnetic ¹H and ¹³C NMR spectra were analyzed comprehensively. The experimental ¹³C—¹H coupling values are temperature (T^?1)‐ as well as magnetic‐field (B²)‐dependent and deviate considerably from typical scalar ¹J_CH couplings constants. This deviation is attributed to residual dipolar couplings (RDCs), which arise from partial alignment of the complexes in the presence of a strong magnetic field. The analysis of the experimental RDCs allows an unambiguous assignment of all ¹³C NMR resonances and, additionally, a structural refinement of the conformation of the complexes in solution. Moreover the RDCs can be used for the analysis of the alignment tensor and hence the tensor of the anisotropy of the magnetic susceptibility.