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Ch.21 - Transition Elements and Coordination Chemistry
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
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.

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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.
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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.
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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.
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Related Practice
Textbook Question

Assign a systematic name to each of the following ions.  

(a) [AuCl4]-

(b) [Fe(CN)6]4-

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Textbook Question

For each of the following complexes, describe the bonding using valence bond theory. Include orbital diagrams for the free metal ion and the metal ion in the complex. Indicate which hybrid orbitals the metal ion uses for bonding, and specify the number of unpaired electrons. 

(a) [AuCl4]2 (square planar)

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Textbook Question

Tell how many diastereoisomers are possible for each of the following complexes, and draw their structures. 

(a) Pt(NH3)3Cl (square planar) 

(b) [FeBr2Cl2(en)]-

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Textbook Question

Nickel(II) complexes with the formula NiX2L2, where X− is Cl− or N-bonded NCS− and L is the monodentate triphenylphosphine ligand P(C6H5)3, can be square planar or tetrahedral.

(a) Draw crystal field energy-level diagrams for a square planar and a tetrahedral nickel(II) complex, and show the population of the orbitals.

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Textbook Question

Draw a crystal field energy-level diagram, and predict the number of unpaired electrons for each of the following: 

(a) [Mn(H2O)6]2+

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Textbook Question

Which of the following complexes are diamagnetic?

(a) [Ni(H2O)6]2+

(b) [Co(CN)6]3-

(c) [HgI4]2- (tetrahedral) 

(d) [Cu(NH3)4]2+ (square planar) 

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