Skip to main content
Pearson+ LogoPearson+ Logo
Ch.21 - Transition Elements and Coordination Chemistry
All textbooksMcMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.140a
Chapter 21, Problem 21.140a

Cobalt(III) trifluoroacetylacetonate, Co(tfac)3, is a sixc oordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:
(a) Draw all possible diastereoisomers and enantiomers of Co(tfac)3.

Verified step by step guidance
1
Step 1: Understand the structure of the complex. Cobalt(III) trifluoroacetylacetonate, Co(tfac)3, is an octahedral complex with three bidentate ligands. Each tfac ligand coordinates to the cobalt center through two donor atoms, forming a chelate ring.
Step 2: Recognize that the octahedral geometry allows for different spatial arrangements of the ligands. In this case, the ligands are identical, so we need to consider the possible arrangements that lead to different stereoisomers.
Step 3: Identify the possible diastereoisomers. In an octahedral complex with three identical bidentate ligands, there are two main types of isomers: facial (fac) and meridional (mer). The fac isomer has all three ligands occupying adjacent positions, while the mer isomer has them spread out, with one ligand opposite the other two.
Step 4: Consider the enantiomers. Enantiomers are non-superimposable mirror images. In the case of Co(tfac)3, the fac isomer can have enantiomers because it lacks a plane of symmetry, whereas the mer isomer is typically achiral.
Step 5: Draw the structures. For the fac isomer, draw two mirror image structures to represent the enantiomers. For the mer isomer, draw a single structure, as it does not have enantiomers. Ensure that the drawings clearly show the spatial arrangement of the ligands around the cobalt center.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

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

Coordination Chemistry

Coordination chemistry involves the study of complex compounds formed between metal ions and ligands. In this context, cobalt(III) is the central metal ion, and the trifluoroacetylacetonate (tfac) ligands are bidentate, meaning each ligand can form two bonds with the metal. Understanding the geometry and bonding of these complexes is crucial for analyzing their stereochemistry.
Recommended video:
Guided course
00:27
Coordination Numbers

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. In the case of Co(tfac)3, the arrangement of the bidentate ligands around the cobalt center can lead to different spatial configurations, resulting in diastereoisomers and enantiomers, which are essential for understanding the compound's chemical behavior.
Recommended video:
Guided course
01:56
Stereoisomers

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, akin to left and right hands. In coordination complexes like Co(tfac)3, chirality arises when the arrangement of ligands creates distinct enantiomers. Identifying chiral centers and understanding their implications is vital for drawing the correct stereoisomers and recognizing their potential optical activity.
Recommended video:
Guided course
02:37
Chirality
Related Practice
Textbook Question

The complete reaction of 2.60 g of chromium metal with 50.00 mL of 1.200 M H2SO4 in the absence of air gave a blue solution and a colorless gas that was collected at 25°C and a pressure of 735 mm Hg. (e) When an excess of KCN is added to the solution, the color changes, and the paramagnetism of the solution

decreases. Explain.

Textbook Question

In acidic aqueous solution, the complex trans-[Co(en)2Cl1]2+(aq) undergoes the following substitution reaction:

trans-[Co(en)1Cl2]+(aq) + H2O(l) → trans-[Co(en)2(H2O)Cl]2+(aq) + Cl–(aq)

The reaction is first order in trans-[Co(en)2Cl2]+(aq), and the rate constant at 25°C is 3.2×10–5 s–1.

(d) Is the reaction product chiral or achiral? Explain.

Textbook Question

In acidic aqueous solution, the complex trans-[Co(en)2Cl1]2+(aq) undergoes the following substitution reaction:

trans-[Co(en)2Cl1]+(aq) + H2O(l) → trans-[Co(en)2(H2O)Cl]2+(aq) + Cl–(aq)

The reaction is first order in trans-[Co(en)2Cl2]+(aq), and the rate constant at 25°C is 3.2×10–5 s–1.

e. Draw a crystal field energy-level diagram for trans-[Co(en)2Cl2]+ that takes account of the fact that Cl– is a weaker-field ligand than ethylenediamine.

Textbook Question

Cobalt(III) trifluoroacetylacetonate, Co(tfac)3, is a sixcoordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:

(b) Diastereoisomers A and B have dipole moments of 6.5 D and 3.8 D, respectively. Which of your diastereoisomers is A and which is B?

Textbook Question

Cobalt(III) trifluoroacetylacetonate, Co1tfac23, is a sixcoordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:

(d) Draw a crystal field energy-level diagram for Co1tfac23, and predict its magnetic properties. (In this complex, tfac is a strong-field ligand.)

Textbook Question

Based on effective nuclear charge (Zeff), which ion is the strongest oxidizing agent? 

(a) Cu2+

(b) Ni2+

(c) Fe2+

(d) Mn2+