Ch.21 - Transition Elements and Coordination Chemistry

Problem 21.127a

Chapter 21, Problem 21.127a

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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Identify the oxidation state of the metal ion in the complex. For [AuCl_4]^2-, determine the oxidation state of Au.

Determine the electron configuration of the free metal ion. For Au, consider its position in the periodic table and its electron configuration.

Draw the orbital diagram for the free metal ion, showing the distribution of electrons in its d orbitals.

Consider the geometry of the complex (square planar) and determine the hybridization of the metal ion. Identify which orbitals are involved in hybridization.

Draw the orbital diagram for the metal ion in the complex, showing the hybrid orbitals and the number of unpaired electrons.

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Key Concepts

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

Valence Bond Theory

Valence Bond Theory (VBT) explains how atoms in a molecule bond by overlapping their atomic orbitals. It emphasizes the role of hybridization, where atomic orbitals mix to form new hybrid orbitals that can accommodate bonding pairs of electrons. This theory helps in predicting the geometry of molecules based on the types of hybrid orbitals involved.

Hybridization

Hybridization is the process of combining atomic orbitals to create new hybrid orbitals that are suitable for the pairing of electrons to form chemical bonds. In the case of the square planar complex [AuCl4]2-, the gold ion undergoes dsp2 hybridization, utilizing one d orbital, one s orbital, and two p orbitals to form four equivalent hybrid orbitals for bonding.

Unpaired Electrons

Unpaired electrons are electrons that occupy an orbital singly rather than in pairs. The presence of unpaired electrons is crucial for determining the magnetic properties of a complex and its reactivity. In the context of [AuCl4]2-, analyzing the electron configuration of the gold ion before and after hybridization helps identify the number of unpaired electrons, which influences the complex's overall behavior.

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Give a valence bond description of the bonding in each of the following complexes. 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.

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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.

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Textbook Question

There are two possible [M(OH)4]- complexes of first-series transition metals that have three unpaired electrons.

(a) What are the oxidation state and the identity of M in these complexes?

(b) Using orbital diagrams, give a valence bond description of the bonding in each complex.

(c) Based on common oxidation states of first-series transition metals (Figure 21.6), which [M(OH)4]- complex is more likely to exist?

<QUESTION REFERENCES FIGURE 21.6>-

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Textbook Question

Two first-series transition metals have three unpaired electrons in complex ions of the type [MCl4]2-.

(a) What are the oxidation state and the identity of M in these complexes?

(b) Draw valence bond orbital diagrams for the two possible ions.

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