Figure 21.17 shows that the cis isomer of Co(en)2 Cl2^+ is optically active while the trans isom

step 1 So this question is telling us about the cobalt ethylene diamine complex with chloride iron. So

Figure 21.17 shows that the cis isomer of Co(en)2 Cl2^+ is...

Figure $21.17$ shows that the cis isomer of $\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}^{+}$ is optically active while the trans isomer is not optically active. Is the same true for $\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}^{+} ?$ Explain.

Key Concepts

Coordination Complex Geometry

Octahedral coordination complexes consist of a central metal ion surrounded symmetrically by six ligands. The spatial arrangement in these complexes can lead to the presence or absence of symmetry elements, which in turn governs properties like optical activity and isomerism. Understanding the basic geometry is crucial in analyzing how different ligand placements affect chirality.

Geometric Isomerism

Geometric isomerism in coordination compounds involves distinct arrangements of ligands, such as cis and trans configurations. These isomers may differ in symmetry; for example, one isomer can lack a mirror plane making it chiral and optically active, while the other, having symmetry elements, remains achiral. This concept is key to understanding differences in physical properties between isomers.

Chirality and Optical Activity in Coordination Compounds

Chirality in coordination compounds arises when their three?dimensional arrangements lack symmetry elements such as mirror planes or centers of inversion, leading to non-superimposable mirror images. Optical activity, the ability to rotate plane-polarized light, is a direct consequence of this chirality. The phenomenon is central in distinguishing which isomer of a complex will exhibit optical activity.

Chelating versus Monodentate Ligands

Chelating ligands, being bidentate, bind through two donor atoms and often form rings that can lead to inherently chiral arrangements when positioned asymmetrically. In contrast, monodentate ligands, like ammonia, coordinate through a single site and usually distribute symmetrically around the metal center. This distinction explains why a complex with bidentate ligands might display optical isomerism, whereas a similar complex with monodentate ligands may not, even if both have cis configurations.

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