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Ch.23 - Transition Metals and Coordination Chemistry
Chapter 23, Problem 9

In the linear crystal-field shown here, the negative charges are on the z-axis. Using Figure 23.28 as a guide, predict which of the following choices most accurately describes the splitting of the d orbitals in a linear crystal-field? [Find more in Section 23.6.]                                                                                                                                                

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Understand the geometry of the crystal field: In a linear crystal-field, the ligands are aligned along the z-axis, directly influencing the d orbitals along this axis.
Identify the d orbitals affected: The d orbitals that will be most affected are those that have lobes pointing along the z-axis, namely the $d_{z^2}$ orbital.
Consider the effect on other d orbitals: The $d_{x^2-y^2}$, $d_{xy}$, $d_{xz}$, and $d_{yz}$ orbitals will be less affected as their lobes do not point directly along the z-axis.
Predict the splitting pattern: The $d_{z^2}$ orbital will experience a different energy shift compared to the other four d orbitals due to its direct alignment along the z-axis.
Conclude the splitting: In a linear crystal-field, typically the $d_{z^2}$ orbital will have a different energy compared to the other four ($d_{x^2-y^2}$, $d_{xy}$, $d_{xz}$, and $d_{yz}$) which might remain degenerate or split further depending on the specific environment and ligand characteristics.

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Key Concepts

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

Crystal Field Theory

Crystal Field Theory (CFT) explains how the arrangement of ligands around a central metal ion affects the energy levels of the d orbitals. In a crystal field, the presence of negative charges from ligands can cause the d orbitals to split into different energy levels, depending on the geometry of the arrangement. This theory is crucial for understanding the electronic structure and color properties of transition metal complexes.
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01:18
The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.

Orbital Splitting in Linear Fields

In a linear crystal field, the d orbitals split into two distinct energy levels due to the orientation of the ligands along the z-axis. Specifically, the d_{z^2} orbital experiences a higher energy due to direct interaction with the ligands, while the d_{x^2-y^2} orbital is also affected but to a lesser extent. Understanding this splitting is essential for predicting the electronic transitions and magnetic properties of the complex.
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03:04
The crystal field splitting pattern for octahedral complexes has the d orbitals on or along the axes as having the higher energy.

Ligand Field Strength

Ligand field strength refers to the ability of ligands to influence the energy levels of d orbitals in a metal complex. Strong field ligands cause greater splitting of the d orbitals, leading to different electronic configurations and properties compared to weak field ligands. This concept is vital for predicting the stability, color, and reactivity of transition metal complexes in various environments.
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Strong-Field Ligands result in a large Δ and Weak-Field Ligands result in a small Δ.
Related Practice
Textbook Question

Four-coordinate metals can have either a tetrahedral or a square-planar geometry; both possibilities are shown here for [PtCl2(NH3)2].

a. What is the name of this molecule?

b. Would the tetrahedral molecule have a geometric isomer?

c. Would the tetrahedral molecule be diamagnetic or paramagnetic?

d. Would the square-planar molecule have a geometric isomer?

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Open Question
Complete the exercises below. a. A compound with formula RuCl₃ • 5H₂O is dissolved in water, forming a solution that is approximately the same color as the solid. Immediately after forming the solution, the addition of excess AgNO₃ (aq) forms 2 mol of solid AgCl per mole of complex. Write the formula for the compound, showing which ligands are likely to be present in the coordination sphere.
Textbook Question

Which of these crystal-field splitting diagrams represents:

a. a weak-field octahedral complex of Fe³⁺ ,

b. a strong-field octahedral complex of Fe³⁺ 

c. a tetrahedral complex of Fe³⁺

d. a tetrahedral complex of Ni²⁺ (The diagrams do not indicate the relative magnitudes of ∆. ) [Find more in Section 23.6.]

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Open Question
Complete the exercises below. The lanthanide contraction explains which of the following periodic trends? a. The atomic radii of the transition metals first decrease and then increase when moving horizontally across each period. b. When forming ions, the period 4 transition metals lose their 4s electrons before their 3d electrons. c. The radii of the period 5 transition metals (Y–Cd) are very similar to the radii of the period 6 transition metals (Lu–Hg).
Open Question
Complete the exercises below. Which periodic trend is partially responsible for the observation that the maximum oxidation state of the transition-metal elements peaks near groups 7B and 8B? a. The number of valence electrons reaches a maximum at group 8B. b. The effective nuclear charge increases on moving right across each period. c. The radii of the transition-metal elements reach a minimum for group 8B, and as the size of the atoms decreases it becomes easier to remove electrons.
Open Question
Complete the exercises below. For each of the following compounds, determine the electron configuration of the transition-metal ion. a. TiO, b. TiO₂, c. NiO, d. ZnO.