Problem 150 - A Complete Resource Book in Chemistry for JEE Main

Question

The type of isomerism present in nitropentaamine chromium (III) chloride is (a) ionization (b) optical (c) polymerization (d) linkage

Step-by-Step Solution

Answer

The type of isomerism is linkage.

Step 1: Understand the Compound

Nitropentaamine chromium (III) chloride is a coordination compound. The formula can be understood as \[ [Cr(NH_3)_5NO_2]Cl_2 \]. Here, 'NO_2' can be attached to the central metal atom through either nitrogen or oxygen, indicating potential for a specific type of isomerism.

Step 2: Identify Potential Isomerism Types

The types of isomerism in coordination compounds include ionization, coordination, linkage, optical, and geometrical. Given the structure \[ [Cr(NH_3)_5NO_2]Cl_2 \], linkage isomerism is possible because the 'NO_2' group can attach to chromium through either N or O.

Step 3: Confirm Linkage Isomerism

Linkage isomerism occurs when a ligand can coordinate to a metal in multiple ways. In this case, 'NO_2' can link through nitrogen to form a nitrito-N complex or through oxygen to form a nitrito-O complex. This confirms the presence of linkage isomerism.

Key Concepts

Coordination Compounds

Coordination compounds are fascinating chemical entities where a central metal atom or ion is surrounded by molecules or anions called ligands. All ligands are bonded to the metal atom through coordinate covalent bonds. These compounds hold high importance in chemistry due to their unique properties and diverse structures.
They can exhibit a variety of behaviors that depend on the nature of the metal and the ligands. The structure of coordination compounds can vastly influence their chemical and physical properties.

• Metal Center: The central metal can be an atom or ion with vacant orbitals to accept electron pairs.
• Ligands: These are ions or neutral molecules that donate a pair of electrons to the metal center, stabilizing the compound.
• Coordination Number: This refers to the number of ligand attachments or sites around the central metal. It varies widely, but common coordination numbers include 4 and 6.

Coordination compounds are crucial for understanding the complex behaviors of metals in chemical reactions and biological systems.

Isomerism in Coordination Chemistry

Isomerism is a phenomenon where compounds have the same chemical formula but different structures or configurations. In coordination chemistry, this opens up a world of possibilities because the way ligands are arranged around the metal center deeply affects the properties and reactivity of the compound.
There are several types of isomerism seen in coordination compounds:

• Geometrical Isomerism: Occurs when ligands have different spatial arrangements around the metal but are bound in the same way. Common in square planar and octahedral complexes.
• Optical Isomerism: Results from the arrangement of ligands in a manner that that makes the compound non-superimposable on its mirror image, similar to left and right hands.
• Linkage Isomerism: Occurs when a ligand can bond through different atoms to the metal. This is prominent when ligands like the nitrite ion ( O_2^{-} ) can attach either through nitrogen or oxygen.

It is the intricate nature of these isomers that dictate the wide range of applications and functionality in coordination chemistry.

Linkage Isomerism

Linkage isomerism is a specific type of isomerism encountered in coordination compounds. It happens when a particular ligand can attach to the central metal through different atoms. A classic example of linkage isomerism is seen in compounds containing the nitrite ion (NO_2).
In nitrite, the structure can allow the connection either through the nitrogen atom (forming a nitrito-N linkage) or through the oxygen atom (forming a nitrito-O linkage).

• This type of isomerism affects properties such as color, reactivity, and magnetic properties.
• Linkage isomers have identical chemical formulas but differ in the atom of the ligand that is bonded to the metal center.
• It's important because the orientation of the bond to the metal can significantly impact the compound's interaction with other chemicals and its overall stability.

Understanding linkage isomerism is crucial since it not only illustrates the versatility of coordination compounds but also showcases the creativity inherent in designing new compounds with desired properties.