Pure Quadrupole Resonance Study of 59Co, 35Cl, and 37Cl in [Co(NH3)5Cl]2+

The quadrupole coupling constants of ⁵⁹Co and the asymmetry parameters in [Co(NH₃)₅Cl]Cl₂${\mathrm{(e}}^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}31.74}\mathrm{MHz}$ , $\text{η\hspace{0.17em}=\hspace{0.17em}0.251}$ ) and [Co(NH₃)₅Cl]SO₄·H₂SO₄($e^2\text{qQ\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}33.43}$ and 34.39 MHz, $\text{η\hspace{0.17em}=\hspace{0.17em}0.042}$ and 0.089) have been determined. In the latter complex, two inequivalent sites of ³⁵Cl and ³⁷Cl resonances have also been observed. Their resonance frequencies are 15.484 and 15.521 MHz for ³⁵Cl, and 12.203 and 12.232 MHz for ³⁷Cl. The application of the Townes and Dailey method to the chlorine data gives the ionic character of about 67% for the Cl–Co bond. The contributions from the valence electrons of the cobalt and from the ionic charges at the ligands and crystal lattice to the field gradient at the cobalt site are discussed.