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Ch.23 - Transition Metals and Coordination Chemistry
All textbooksBrown 15th EditionCh.23 - Transition Metals and Coordination ChemistryProblem 88
Chapter 23, Problem 88

Complete the exercises below. When Alfred Werner was developing the field of coordination chemistry, it was argued by some that the optical activity he observed in the chiral complexes he had prepared was due to the presence of carbon atoms in the molecule. To disprove this argument, Werner synthesized a chiral complex of cobalt that had no carbon atoms in it, and he was able to resolve it into its enantiomers. Design a cobalt(III) complex that would be chiral if it could be synthesized and that contains no carbon atoms. (It may not be possible to synthesize the complex you design, but we will not worry about that for now.)

Verified step by step guidance
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Step 1: Understand the concept of chirality in coordination complexes. Chirality occurs when a molecule or ion cannot be superimposed on its mirror image, similar to left and right hands.
Step 2: Recognize that for a coordination complex to be chiral, it must lack a plane of symmetry. This often involves having a specific arrangement of ligands around the central metal ion.
Step 3: Consider the coordination number and geometry of cobalt(III) complexes. Cobalt(III) typically forms octahedral complexes with a coordination number of 6.
Step 4: Select ligands that do not contain carbon atoms. Common non-carbon ligands include halides (e.g., Cl⁻, Br⁻), oxides (e.g., O²⁻), and other anions like NO₂⁻ or NH₃.
Step 5: Arrange the selected ligands around the cobalt(III) ion in a way that creates a chiral arrangement. For example, use a combination of different ligands in a cis or trans configuration to achieve chirality.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coordination Chemistry

Coordination chemistry is the study of coordination compounds, which consist of a central metal atom bonded to surrounding molecules or ions called ligands. These complexes can exhibit various geometries and properties, influencing their reactivity and interactions. Understanding the nature of these bonds and the arrangement of ligands is crucial for predicting the behavior of metal complexes, including their chirality.
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Coordination Numbers

Chirality and Enantiomers

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Molecules that exhibit chirality can exist as pairs of enantiomers, which have identical physical properties but differ in their interaction with polarized light and biological systems. The presence of chiral centers, often involving asymmetric arrangements of ligands around a central atom, is essential for the formation of these enantiomers.
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Cobalt(III) Complexes

Cobalt(III) complexes are coordination compounds where cobalt is in the +3 oxidation state, typically forming octahedral geometries with six ligands. The choice of ligands and their spatial arrangement can lead to the formation of chiral complexes. Designing a chiral cobalt(III) complex without carbon atoms requires careful selection of ligands that can create an asymmetric environment around the cobalt center, thus enabling the potential for chirality.
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Related Practice
Textbook Question

The coordination complex [Cr(CO)6] forms colorless, diamagnetic crystals that melt at 90 °C

a. What is the oxidation number of chromium in this compound?

d. Write the name for [Cr(CO)6] using the nomenclature rules for coordination compounds.