Problem 32 - A Complete Resource Book in Chemistry for JEE Main

Question

The IUPAC name for \(\left[\mathrm{Be}_{4} \mathrm{O}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]\) is (a) Basic beryllium acetate(II) (b) hexa-\mu-hexakis (acetato) beryllium(II) (c) hexa- \(\mu\)-acetato \(\left(\mathrm{O}, \mathrm{O}^{\prime}\right)-\mu_{4}\)-oxotetraberyllium(II) (d) hexaacetato- \(\mu\)-oxoberyllium(II)

Step-by-Step Solution

Answer

(c) hexa-\(\mu\)-acetato \((O,O')-\mu_4\)-oxotetraberyllium(II)

Step 1: Understand Compound Structure

The given compound \(\left[\mathrm{Be}_{4} \mathrm{O}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]\) consists of 4 beryllium atoms, an oxygen atom, and 6 acetate groups \(\left(\mathrm{CH}_{3} \mathrm{COO}\right)\). 'Be' is the metal involved, and the chemical formula indicates a central oxygen that bridges the beryllium atoms.

Step 2: Identify the Bridging Groups

The presence of the oxygen (O) atom between beryllium (Be) atoms suggests a bridging nature, which is typical for such clusters. This bridging atom is denoted by \(\mu\), indicating that it is shared between multiple metal centers.

Step 3: Determine Coordination of Acetate Groups

Each acetate (\(\mathrm{CH}_3\mathrm{COO}\)) group acts as a bidentate ligand, using both oxygen atoms. With 6 such groups coordinating with Be, the naming should reflect these bridging and coordinating ligands.

Step 4: Piece Together IUPAC Naming

Recognizing the 4 beryllium atoms and the \(\mu_4\)-oxo bridge, along with acetate groups acting in a coordinating manner, the IUPAC name considers these features. The use of \(mu\) indicates multinuclear bridges, and \(O,O'\) denotes binding sites from the acetate group.

Step 5: Select the Correct IUPAC Name

The correct IUPAC name reflects these observations: hexa-\(\mu\)-acetato \((O,O')-\mu_4\)-oxotetraberyllium(II), which matches with option (c).

Key Concepts

Coordination Chemistry

In coordination chemistry, a central atom or ion—usually a metal—bonds with molecules or ions called ligands. These ligands donate electron pairs to form coordination complexes. The central atom is known as the coordination center and can have multiple ligands attached, defining the coordination number. This branch of chemistry is vital because coordination compounds exhibit unique chemical properties and reactivities.

When examining coordination in compounds like \(\left[\mathrm{Be}_{4} \mathrm{O}\left(\mathrm{CH}_{3}\mathrm{COO}\right)_{6}\right]\), it's crucial to note the roles and impacts of different ligands. Here, the acetate groups act as ligands, and they play a central role in forming the structure and stability of such complexes.

• Central atoms like beryllium often use empty orbitals to accept ligand electrons.
• Bidentate ligands like acetates use two atoms to bind, influencing the geometry and coordination number.

Understanding how ligands coordinate helps in predicting the geometry, reactivity, and overall properties of the compound.

Bridging Ligands

Bridging ligands are a fascinating aspect of coordination chemistry. These ligands connect two or more metal centers, playing a crucial role in stabilizing metal clusters. In the given compound, \(\left[\mathrm{Be}_{4} \mathrm{O}\left(\mathrm{CH}_{3}\mathrm{COO}\right)_{6}\right]\), the oxygen atom serves as a bridge between beryllium atoms.

The notation \(\mu\) is used to denote these bridging ligands in nomenclature, indicating shared functionality across different metal centers.

• Bridging increases stability by reducing strain and allowing delocalization of electrons.
• Commonly used bridging atoms are oxygen, nitrogen, and halides due to their ability to form multiple bonds.

In this compound, \(\mu_4\)-oxo suggests the oxygen bridges four beryllium atoms, contributing to the complex's overall stability and shape.

Metal Clusters

Metal clusters consist of groups of metal atoms bonded together, as seen in the \(\left[\mathrm{Be}_{4} \mathrm{O}\left(\mathrm{CH}_{3}\mathrm{COO}\right)_{6}\right]\) complex. Metal clusters are an intriguing area of study due to their diverse properties and potential applications.

Clusters are often stabilized by bridging ligands and can range from simple dimers to large networks comprising dozens of atoms. In our compound, the presence of four beryllium atoms and a bridging oxygen forms a stable cluster.

• These clusters often exhibit distinct electronic, magnetic, and catalytic properties.
• Their study aids in understanding metal-metal bonding and advances in synthetic chemistry.

The IUPAC naming process for such clusters involves reflecting these structures with terms like \(\mu\)-bridges and specifying the number of metals involved, as seen in tetraberyllium, where four metal atoms are unified into a distinct structural unit.