Carbones (–C2−–), carbenes (–C:–) and carbodications (–C2+–) on the magnetic criterion

Abstract

The spatial magnetic properties, particularly the through-space NMR shieldings (TSNMRSs, the anisotropy effect in ¹H NMR spectroscopy) of carbenes, carbones and carbodication (carbo2+) compounds (with and without stabilization by NMe₂ π-donation) and those of a number of carbo2+ analogues have been calculated using the GIAO perturbation method, employing the nucleus-independent chemical shift (NICS) concept, and visualized as iso-chemical-shielding surfaces (ICSS) of various sizes and directions. TSNMRSs prove the electronic structure of carbo2+ compounds to be completely different from those of carbenes and carbones, preferring both the π-electron distribution and the structure of allenes/cumulenes despite the central carbon atom being the most electrophilic centre.