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 ($e^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}165.6}\mathrm{Mc}/\sec )$ one shift tensor component was used to obtain an improved gyromagnetic ratio for ⁵⁹Co: $\text{γ\hspace{0.17em}=\hspace{0.17em}1.0035}\mathrm{kc}/\sec ·\mathrm{G}$ . For the substituted octahedral complexes trans‐[Co en₂Cl₂]Cl·HCl·2H₂O ${\mathrm{(e}}^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}71.7}\mathrm{Mc}/\sec )$ ; [Co(NH₃)₅CN]Cl₂ ${\mathrm{(e}}^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}26.6}\mathrm{Mc}/\sec )$ ; [Co(NH₃)₄CO₃]Br ${\mathrm{(e}}^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}18.8}\mathrm{Mc}/\sec$ ; and trans‐[Co en₂(NO₂)₂]NO₃ ${\mathrm{(e}}^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}13.2}\mathrm{Mc}/\sec )$ , a linear dependence of the shift anisotropy ${\mathrm{(\sigma }}_{\mathrm{zz}}{\mathrm{-\sigma }}_{\mathrm{yy}}\text{\hspace{0.17em}=\hspace{0.17em}+\hspace{0.17em}4.6‰}$ , − 2.2‰, + 1.5‰, and + 0.4‰) on the quadrupole coupling constant was found. The molecular orbital theory was used to interpret the results.