Question

The complex ion \(\mathrm{PdCl}_{4}{ }^{2-}\) is diamagnetic. Propose a structure for \(\mathrm{PdCl}_{4}^{2-}\)

Short answer

The proposed structure for the \(\mathrm{PdCl}_{4}^{2-}\) complex ion is square planar, with the central palladium atom surrounded by four chloride ions at the corners of a square. This structure allows all electrons to be paired, resulting in a diamagnetic complex.

Step-by-step solution

Electron Configuration of Palladium and Chlorine

Determine the electron configuration of palladium (Pd) and chlorine (Cl). The electron configuration of Pd is [Kr]4d\(^{10}\)5s\(^0\), and for Cl, it is [Ne]3s\(^2\)3p\(^5\). Since we have a 2- charge on the complex ion, that means palladium will donate two electrons to form bonds with the four chlorines.

Formation of Coordination Bonds

The Pd atom will form coordination bonds with four Cl atoms, with each chlorine donating one electron to form the bond. Since each Cl has one unpaired electron in its 3p orbital, the Pd atom can accommodate the electron from each chlorine, making a total of four coordination bonds within the complex.

Structure and Geometry of the Complex

The \(\mathrm{PdCl}_{4}^{2-}\) complex has a central palladium atom surrounded by four chloride ions. Considering that the square planar geometry is common for complexes with a coordination number of 4, it is most likely that the structure of the \(\mathrm{PdCl}_{4}^{2-}\) complex will also be square planar. In this geometry, all four chloride ions are positioned in the same plane as the central palladium atom, with each chloride ion at the corners of a square and the palladium atom at the center.

Confirmation of Diamagnetism

in the proposed square planar structure, all electrons are paired up in the \(\mathrm{PdCl}_{4}^{2-}\) complex. Palladium donates two electrons, one to each of two chlorines. Now all chlorines have a complete 3p orbital. Since there are no unpaired electrons, the complex is diamagnetic, which matches the given information. In conclusion, the proposed structure for the \(\mathrm{PdCl}_{4}^{2-}\) complex ion is square planar with all electrons paired, resulting in a diamagnetic complex.

Key concepts

Complex Ions

Complex ions are fascinating constructs in coordination chemistry. They are positively or negatively charged species, composed of a central metal ion bonded to a group of molecules or ions called ligands. These ligands, which can be atoms, ions, or molecules, donate electron pairs to form what are known as coordination bonds with the central metal ion. For example, in the complex ion \(\mathrm{PdCl}_{4}^{2-}\), the central palladium ion forms bonds with four chlorine ligands. The charge on the complex comes from the metal ion and the ligands combined. Key Points About Complex Ions:

• The central metal ion, like Pd in this case, accepts electron pairs.
• Ligands donate electron pairs to form coordination bonds.
• The charge of the complex ion is the sum of the metal ion and ligands' charges.

This concept is fundamental in understanding how coordination compounds interact and behave chemically.

Square Planar Geometry

Square planar geometry is a common structure in coordination chemistry, particularly for complexes with a coordination number of four. In this geometry, four ligands are symmetrically arranged in a square around a central metal atom, all lying in the same plane. For \(\mathrm{PdCl}_{4}^{2-}\), the central palladium atom is surrounded by four chloride ions at the corners of a square, leading to its square planar geometry. This arrangement promotes stability and symmetry, making it a favorable configuration.Characteristics of Square Planar Geometry:

• Central metal ion residing at the center of a square.
• All ligand atoms lie in the same plane.
• Commonly observed in transition metals, like palladium and platinum complexes.

Understanding this geometry is crucial for visualizing and predicting the behavior of such complex ions.

Diamagnetism

Diamagnetism is a property of materials that causes them to be repelled by a magnetic field. It arises in substances where all electron spins are paired and there are no unpaired electrons.In the case of \(\mathrm{PdCl}_{4}^{2-}\), the complex is diamagnetic because the palladium atom forms bonds in a way that pairs all available electron spins. When there are no unpaired electrons in the molecular configuration, the complex does not respond to magnetic fields.Important Aspects of Diamagnetism:

• Occurs in materials with all electrons paired.
• Results in a weak repulsion from magnetic fields.
• Indicative of stable electron configurations in complex ions.

This property of diamagnetism in \(\mathrm{PdCl}_{4}^{2-}\) confirms the stability of its square planar configuration.

Palladium Coordination Bonds

Palladium, a transition metal, is renowned for its ability to form strong coordination bonds with various ligands. In \(\mathrm{PdCl}_{4}^{2-}\), the palladium ion forms bonds with chloride ions, each contributing an electron to establish a robust coordination environment. The electron configuration of palladium, \([Kr]4d^{10}5s^0\), indicates that it can use its 4d orbitals to accept electrons from ligands like chlorine. This enables palladium to hold the ligands tightly, forming a stable square planar complex.Insights on Palladium Coordination Bonds:

• Utilizes empty d-orbitals to form bonds.
• Forms stable complexes with a variety of ligands.
• Key component in catalytic and electron-sharing reactions.

The nature of palladium's coordination bonds is essential in its reactivity and applications in both chemical and industrial processes.