Study Guide to Transitions Metal Chemistry

---

DISCLAIMER: This Guide is not meant to be exhaustive. That is, I have tried to summarize the essential points of the lectures on this topic. The presence of a topic here does not guarantee a related question on an exam, nor are exam topics limited to what appears in this Guide. As with any Chemistry class, you are responsible for ALL of the assigned readings, problems and lecture material. Lectures will often contain information not covered or given less emphasis in the text.

---

Text Reading

Chapter 20 (Sections 1, 3, 4 and 6)
pages 930-937, 943-948, 948-955 and 957-964

What should you learn from this section of the course?

Our emphasis continues to be chemical bonding. In this case, we encounter a new type of molecule, the coordination complex. It is not essential to memorize nomenclature. I'll provide structures for all molecules. That does not mean you should ignore the material on nomenclature, but don't try to memorize it. In general, you should be aware of the crystal field model for bonding in octahedral and tetrahedral complexes covered in class, as well as simple extensions to other types of structures. You should also be confident in describing the physical properties of these compounds, such as spin, paramagnetism, color, etc.

General

• Definitions of important new terms such as coordination number, ligand, chelate
• Convention for writing molecular formula (complex ion, consisting of metal plus ligands, in square brackets and counter ion outside), but no need to memorize specific nomenclature.
• Familiarity with geometric isomers

Structures

• Be able to write structures with correct geometry, given the coordination number
• Be comfortable with the concept of chirality (handedness)

Bonding

• Understand crystal field theory and the elimination of energy level degeneracy
• Understand the relationship of low spin and high spin to electron configuration
• Understand how the data can be collected into the spectrochemical series

Recommended Chapter 20 Problems

General: 9. Coordination compounds: 17, 23, 31. Bonding: 37, 39, 41, 43, 45. Mixed concepts:51

Additional Problems

1. Determine the number of unpaired electrons in the complex [Cr(NH₃)₆]³⁺.

2. The complex [NiCl₄]^2- has two unpaired electrons, while [Ni(CN)₄]^2- is diamagnetic. Explain these observations using crystal field theory.

3. The crystal field splitting of [Mn(H₂O)₆]³⁺, a high spin octahedral complex, is 250 kJ/mole and that of [Mn(CN)₆]^3-, a low spin complex is 460 kJ/mole. (a) Write the d electron configuration for each of these complexes and give the number of unpaired electrons; (b) would you expect [Mn(OH)₆]^3- to be high or low spin?

4. The diamagnetic complex [Co(NH₃)₆]³⁺ is orange yellow, while the paramagnetic complex [CoF₆]^3- is blue. Explain the color difference.

Return to: Chem 6 Home Page