The 13 C chemical shift and the anisotropy effect of the carbene electron-deficient centre: Simple means to characterize the electron distribution of carbenes

Erich Kleinpeter; Andreas Koch

doi:10.1002/mrc.4979

The ¹³ C chemical shift and the anisotropy effect of the carbene electron-deficient centre: Simple means to characterize the electron distribution of carbenes

Magn Reson Chem. 2020 Mar;58(3):280-292. doi: 10.1002/mrc.4979. Epub 2020 Jan 6.

Authors

Erich Kleinpeter¹, Andreas Koch¹

Affiliation

¹ Institut für Chemie, Universität Potsdam, Potsdam, Germany.

PMID: 31828861
DOI: 10.1002/mrc.4979

Abstract

Both the ¹³ C chemical shift and the calculated anisotropy effect (spatial magnetic properties) of the electron-deficient centre of stable, crystalline, and structurally characterized carbenes have been employed to unequivocally characterize potential resonance contributors to the present mesomerism (carbene, ylide, betaine, and zwitter ion) and to determine quantitatively the electron deficiency of the corresponding carbene carbon atom. Prior to that, both structures and ¹³ C chemical shifts were calculated and compared with the experimental δ(¹³ C)/ppm values and geometry parameters (as a quality criterion for obtained structures).

Keywords: 13C chemical shift; carbene electron deficiency; carbenes/zwitterions; nucleus-independent chemical shifts (NICS); through space NMR shieldings (TSNMRS).