Specify the number of unpaired electrons in [Co(NH₃)₆]³⁺ (strong field). A) 2 B) 5 C) 0 D) 4 E) 7

Question

Quizplus · Accepted Answer

The given coordination compound is a complex of cobalt with three different ligand groups: NH₃ (histamine), ₆ (cysteine) and a chelating sulfate ion (S1U1P2O4S1U1P2O7S1U1P2O7). The coordination number of the central cobalt ion is 6, and the complex ion carries a charge of +3. In order to determine the number of unpaired electrons in the complex, we need to find its electronic configuration for the central cobalt ion. Since it is a strong field complex, we can use the crystal field theory to predict that all the ligands will cause a strong splitting of the d-orbitals. The three histamine ligands are expected to cause a relatively small splitting (since they are neutral and weak field), whereas the cysteine and sulfate ligands are strong field and therefore will lead to greater splitting. One possible way to assign d-electrons to the central cobalt ion is to start filling the d-orbitals from the lowest energy level (i.e., the one closest to the ligands), and filling them up in order of increasing energy. Using this approach, we can account for the three unpaired electrons through the following configuration: d_xy2 d_yz1 d_zx1 d_x2-y2 d_z2 d_x2-y21 This electronic configuration has three unpaired electrons, corresponding to the d_xy, d_yz, and d_zx orbitals. The correct answer is therefore (C) 0, since all the d-orbitals in the complex are paired up.

Specify the Number of Unpaired Electrons in [Co(NH3)6]3+ (Strong Field)

Specify the Number of Unpaired Electrons in [Co(NH₃)₆]³⁺ (Strong Field)