Problem 114 - A Complete Resource Book in Chemistry for JEE Main

Question

The hybridization of \(\mathrm{Cu}\) in \(\left[\mathrm{CuCl}_{4}\right]^{2-}\) and \(\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\) are respectively. (a) \(\mathrm{sp}^{3}, \mathrm{dsp}^{2}\) (b) \(\mathrm{dsp}^{2}, \mathrm{dsp}^{2}\) (c) \(\mathrm{dsp}^{2}, \mathrm{sp}^{3}\) (d) \(s p^{3}, s p^{3}\)

Step-by-Step Solution

Answer

(a) \(\mathrm{sp}^{3}, \mathrm{dsp}^{2}\)

Step 1: Understanding Hybridization Concepts

Hybridization refers to the mixing of atomic orbitals to form new hybrid orbitals. For determining hybridization in coordination complexes, we consider the central metal atom's electronic configuration and the type of ligands and their electron pairs.

Step 2: Determine the Hybridization of \(\left[\mathrm{CuCl}_{4}\right]^{2-}\)

The \(\left[\mathrm{CuCl}_{4}\right]^{2-}\) complex involves \(\mathrm{Cu}^{2+}\), which has an electronic configuration of \([\mathrm{Ar}] 3d^9\). Chloride ions (\(\mathrm{Cl}^{-}\)) are weak field ligands, leading to no promotion of electrons from the \(3d\) orbitals. Thus, \([\mathrm{CuCl}_{4}]^{2-}\) uses the \(4s\) and \(3p\) orbitals for hybridization, resulting in \(\mathrm{sp}^{3}\) hybridization.

Step 3: Determine the Hybridization of \(\left[\mathrm{Cu}(\mathrm{NH}_{3})_{4}\right]^{2+}\)

In the \(\left[\mathrm{Cu}(\mathrm{NH}_{3})_{4}\right]^{2+}\) complex, ammonia (\(\mathrm{NH}_{3}\)) is a strong field ligand. It causes pair-up of the \(3d\) electrons and promotes available electrons to the \(4s\) and \(4p\) orbitals. The hybridization involves two \(3d\) and \(4p\) orbitals, leading to \(\mathrm{dsp}^2\) hybridization.

Step 4: Evaluate the Options and Choose the Correct Answer

The hybridization for \([\mathrm{CuCl}_{4}]^{2-}\) is \(\mathrm{sp}^{3}\), and for \([\mathrm{Cu}(\mathrm{NH}_{3})_{4}]^{2+}\) is \(\mathrm{dsp}^{2}\). Comparing these results to the given options, the correct pair is option (a): \(\mathrm{sp}^{3}, \mathrm{dsp}^{2}\).

Key Concepts

Hybridization

Hybridization is a fundamental concept in coordination chemistry. It describes the way atomic orbitals mix to create new hybrid orbitals. These hybrid orbitals can then form chemical bonds with other atoms or ions. Understanding hybridization is crucial for predicting molecule shapes and the arrangement of electrons in complex structures.
When determining the hybridization state of a metal complex, consider the central metal atom's electronic configuration. The nature of the ligands and their interaction with the metal also plays a significant role. Ligands can be either weak-field or strong-field.

• Weak-field ligands, like chloride ions, do not strongly promote the pairing of d-electrons, often leading to sp or sp³ hybridization.
• Strong-field ligands, like ammonia, can cause d-electron pairing, resulting in dsp² hybridization.

Applying these principles helps us understand the hybridizations seen in coordination complexes, such as those formed with copper.

Coordination Complexes

Coordination complexes are structures formed when a central metal atom or ion bonds with surrounding ligands. These ligands can be ions or neutral molecules. The interaction between metal ions and ligands stabilizes the complex and can influence the properties of the complex, such as its color, magnetic properties, and reactivity.
The coordination number reflects how many ligand bonds are attached to the central metal. For example, a tetrahedral complex like \([\mathrm{CuCl}_{4}]^{2-}\) has a coordination number of four. This number indicates the spatial configuration of the ligands around the metal and influences the complex's geometry.

• Tetrahedral complexes typically involve sp³ hybridization and are usually associated with weak-field ligands.
• Square planar complexes involve dsp² hybridization, often resulting from the presence of strong-field ligands.

Coordination chemistry provides a rich framework for understanding how metals interact with ligands, as seen in complex structures.

Copper Complexes

Copper, as a metal, forms a variety of coordination complexes exhibiting different geometries and hybridizations. The oxidation state of copper and the type of ligands attached to it play crucial roles in defining these characteristics.
In \([\mathrm{CuCl}_{4}]^{2-}\), the copper exists in a +2 oxidation state, which means it has lost two electrons. The chloride ligands are weak, and the resulting complex is tetrahedral in shape. This results in sp³ hybridization where copper uses one s and three p orbitals for bonding.
Conversely, \([\mathrm{Cu}(\mathrm{NH}_3)_{4}]^{2+}\) illustrates copper's versatility. Here, ammonia acts as a strong-field ligand. The strong field effect leads to electron pairing and the utilization of dsp² hybridization. This change creates a square planar geometry around the copper ion.

• Copper's ability to form different complex shapes is key in its applications, from industrial catalysis to biological systems.
• The complex's geometric arrangement also affects its electronic properties, including color and magnetic behavior.

Understanding these copper complexes exemplifies the diverse chemistry seen with transition metals.