Ch.23 - Transition Metals and Coordination Chemistry

Problem 8

Chapter 23, Problem 8

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.]

Verified step by step guidance

Identify the electron configuration of Fe³⁺ and Ni²⁺. Fe³⁺ has an electron configuration of 3d^5, and Ni²⁺ has an electron configuration of 3d^8.

Understand the concept of crystal field splitting in different geometries. In octahedral complexes, the d-orbitals split into two energy levels: t2g (lower energy) and eg (higher energy). In tetrahedral complexes, the splitting is reversed with eg (lower energy) and t2g (higher energy).

For a weak-field octahedral complex of Fe³⁺, the electrons will fill the t2g and eg orbitals according to Hund's rule and the Aufbau principle, with minimal pairing due to the lower crystal field splitting energy.

For a strong-field octahedral complex of Fe³⁺, the electrons will first fill the lower energy t2g orbitals completely before occupying the higher energy eg orbitals, showing more electron pairing due to higher crystal field splitting energy.

For tetrahedral complexes of Fe³⁺ and Ni²⁺, distribute the electrons in the eg and t2g orbitals according to their respective electron configurations, considering the reversed order of energy levels compared to octahedral complexes.

Verified Solution

Video duration:

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.

Crystal Field Theory

Crystal Field Theory (CFT) explains the electronic structure of transition metal complexes by considering the interaction between the metal ion's d-orbitals and the electric fields produced by surrounding ligands. This theory helps predict the splitting of d-orbitals into different energy levels, which is crucial for understanding the color, magnetism, and stability of the complexes.

Octahedral vs. Tetrahedral Complexes

In coordination chemistry, octahedral complexes have six ligands symmetrically arranged around a central metal ion, leading to a specific pattern of d-orbital splitting. Tetrahedral complexes, on the other hand, have four ligands and exhibit a different splitting pattern. The geometry of the complex significantly influences the energy difference between the split d-orbitals, denoted as Δ.

Weak-field vs. Strong-field Ligands

Ligands can be classified as weak-field or strong-field based on their ability to split the d-orbitals. Weak-field ligands cause a small splitting (Δ), leading to high-spin configurations, while strong-field ligands cause larger splitting, resulting in low-spin configurations. The nature of the ligands affects the electronic arrangement of the metal ion, influencing the properties of the complex.

Recommended video:

Guided course

02:40

Strong-Field Ligands result in a large Δ and Weak-Field Ligands result in a small Δ.

Related Practice

Open Question

Draw the structure for Pt (en) Cl₂ and use it to answer the following questions: a. What is the coordination number for platinum in this complex? b. What is the coordination geometry? c. What is the oxidation state of the platinum? d. How many unpaired electrons are there? [Find more in Sections 23.2 and 23.6.]

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?

121

views

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

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.]

107

views

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.