Until the discoveries of Alfred Werner, it was thought that carbon had to be present in a compound for it to be optically active. Werner prepared the following compound containing OH⁻ ions as bridging groups and separated the optical isomers.

a. Draw structures of the two optically active isomers of this compound.

b. What are the oxidation states of the cobalt ions?

c. How many unpaired electrons are present if the complex is the low-spin case?

Interpretation: The optically active isomers of the given compound are to be drawn. Oxidation state of the cobalt ions and the number of unpaired electrons present if the complex is the low spin are to be stated.

Concept introduction: The electrons in the d orbital of a transition metal split into high and low energy orbitals when ligands are attached to it. The energy difference between these two levels depends upon the properties of both metal and the ligands. If the ligand is strong, then splitting will be high and the complex will be low spin. If the ligand is weak, then splitting will be less and the complex will be high spin.

To determine: The optically active isomers of the given compound.

The optically active isomers of the given compound are shown in Figure 1.

The optical isomers of the given compound are,

Interpretation: The optically active isomers of the given compound are to be drawn. Oxidation state of the cobalt ions and the number of unpaired electrons present if the complex is the low spin are to be stated.

Concept introduction: The electrons in the d orbital of a transition metal split into high and low energy orbitals when ligands are attached to it. The energy difference between these two levels depends upon the properties of both metal and the ligands. If the ligand is strong, then splitting will be high and the complex will be low spin. If the ligand is weak, then splitting will be less and the complex will be high spin.

To determine: The oxidation states of cobalt ions in the compound.

Interpretation: The optically active isomers of the given compound are to be drawn. Oxidation state of the cobalt ions and the number of unpaired electrons present if the complex is the low spin are to be stated.

Concept introduction: The electrons in the d orbital of a transition metal split into high and low energy orbitals when ligands are attached to it. The energy difference between these two levels depends upon the properties of both metal and the ligands. If the ligand is strong, then splitting will be high and the complex will be low spin. If the ligand is weak, then splitting will be less and the complex will be high spin.