Anisotropic Chemical Shifts in Cobalt (III) Complexes

Abstract

The 59Co NMR was studied in single crystals of a number of cobalt (III) complexes at room temperature. A procedure was developed for the numerical analysis of the spectra, and the chemical shift and quadrupole coupling tensors were determined. In cobaltocenium nitrate (e2qQ / h = 165.6 Mc/sec) one shift tensor component was used to obtain an improved gyromagnetic ratio for 59Co: γ = 1.0035 kc/sec·G. For the substituted octahedral complexes trans-[Co en2Cl2]Cl·HCl·2H2O (e2qQ / h = 71.7 Mc/sec); [Co(NH3)5CN]Cl2 (e2qQ / h = 26.6 Mc/sec); [Co(NH3)4CO3]Br (e2qQ / h = 18.8 Mc/sec; and trans-[Co en2(NO2)2]NO3 (e2qQ / h = 13.2 Mc/sec), a linear dependence of the shift anisotropy (σzz−σyy = + 4.6‰, − 2.2‰, + 1.5‰, and + 0.4‰) on the quadrupole coupling constant was found. The molecular orbital theory was used to interpret the results.