Question

Qualitatively draw the crystal field splitting of the \(d\) orbitals in a trigonal planar complex ion. (Let the \(z\) axis be perpendicular to the plane of the complex.)

Short answer

In a trigonal planar complex ion, the crystal field splitting diagram of the d orbitals is as follows: The highest energy orbitals are \(d_{xy}\) and \(d_{x^2-y^2}\) since they lie in the xy plane and interact the most with the ligands. The \(d_{xz}\) and \(d_{yz}\) orbitals have intermediate energy levels due to their lesser interaction with the ligands. The lowest energy level is occupied by the \(d_{z^2}\) orbital, which points along the z axis and has the least interaction with the ligands. Draw the diagram accordingly to represent the relative energy levels of the d orbitals in a trigonal planar complex ion.

Step-by-step solution

Understand the geometry of the trigonal planar complex ion

The trigonal planar complex ion has a flat, triangular geometry with the central metal ion surrounded by three ligands. The ligands are located at the corners of an equilateral triangle, and the central metal ion is at the center of this triangle. The z axis is perpendicular to the plane of the complex, with the xy plane being the plane of the complex.

Know the d orbitals

There are five d orbitals in total: \(d_{xy}\), \(d_{xz}\), \(d_{yz}\), \(d_{x^2-y^2}\), and \(d_{z^2}\). Each orbital has a unique spatial orientation, and they will interact differently with the ligands in the complex.

Identify the interaction of d orbitals with the ligands

In a trigonal planar complex, the ligands approach the metal ion along the x and y axes. Consequently, the d orbitals that have more interaction with the ligands experience a higher repulsion, leading to a higher energy state. The \(d_{xy}\) and \(d_{x^2-y^2}\) orbitals lie in the xy plane and interact more with the ligands. The \(d_{z^2}\) orbital is oriented along the z axis and interacts less with the ligands. The \(d_{xz}\) and \(d_{yz}\) orbitals are in-between and have an intermediate interaction with the ligands, resulting in an intermediate energy.

Draw the crystal field splitting diagram

Considering the interaction of d orbitals with the ligands, the crystal field splitting diagram for the trigonal planar complex ion is as follows: 1. The highest energy d orbitals are \(d_{xy}\) and \(d_{x^2-y^2}\), lying in the xy plane, and these orbitals have the strongest interaction with the ligands. 2. The intermediate energy d orbitals are \(d_{xz}\) and \(d_{yz}\), which experience lesser interaction with the ligands. 3. The lowest energy level is occupied by the \(d_{z^2}\) orbital, which points along the z axis and has the least interaction with the ligands. Now, you can draw the crystal field splitting diagram with these energy levels, representative of the spatial orientation and interaction of the d orbitals in a trigonal planar complex ion.