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 \((\mathrm{O}, \mathrm{O}')\)-\mu_{4}\)-oxotetraberyllium(II)

Step 1: Understand the Compound Structure

The given compound is \([\text{Be}_4 \text{O}(\text{CH}_3\text{COO})_6]\). It consists of a central \(\text{O}\) atom bonded to four \(\text{Be}\) atoms in a tetrahedral arrangement. Each \(\text{Be}\) is further bonded to six acetate (\(\text{CH}_3\text{COO}^-\)) groups.

Step 2: Determine the Naming System

In IUPAC nomenclature for coordination compounds, we describe the metal core and its coordination environment. 'hexa', 'acetato', and 'oxotetraberyllium(II)' indicates the presence of six acetate groups coordinated to a tetrahedral cluster consisting of four beryllium atoms and a central oxo ligand.

Step 3: Interpret the Components

'hexakis' is used to denote multiple acetate groups, and 'mu' (\(\mu\)) designates bridging ligands in a polynuclear complex. The oxo group bridges all four Be centers, hence the term \(\mu_4\)-oxo.

Step 4: Identify the Correct Name

Considering Steps 1-3, 'hexa-\(\mu\)-acetato \((\text{O}, \text{O}')\)-\(\mu_4\)-oxotetraberyllium(II)' accurately describes the compound. It details the placement and role of ligands, the bridging nature of the oxo group, and the metal's oxidation state.

Key Concepts

Coordination Compounds

Coordination compounds are complex structures consisting of a central metal atom or ion surrounded by molecules or anions called ligands. In the given compound \([\text{Be}_4 \text{O}(\text{CH}_3\text{COO})_6]\), beryllium (\(\text{Be}\)) acts as the central metal atom, forming a complex with several acetate ligands. These ligands donate pairs of electrons to the metal, creating a coordinate covalent bond.

Understanding coordination compounds involves recognizing the coordination environment, which includes the number and types of ligands, the spatial arrangement around the central atom, and the overall connectivity of the structure. This insight is crucial for naming these compounds according to IUPAC conventions.

Oxidation State

The oxidation state of an element within a compound is an indicator of the number of electrons lost or gained by an atom. In coordination chemistry, the oxidation state of the metal is important for determining the compound's properties and its correct nomenclature.

In our example \([\text{Be}_4 \text{O}(\text{CH}_3\text{COO})_6]\), beryllium typically exhibits a +2 oxidation state. This is denoted by the (II) in the compound's name. The oxidation state helps identify how electrons are distributed in the compound and is usually determined by considering the charges of the ligands and the overall charge of the complex.

Bridging Ligands

Bridging ligands are a special class of ligands that connect two or more metal centers within a coordination compound. These ligands can help form polynuclear complexes, which involve multiple metal atoms.

In the compound \([\text{Be}_4 \text{O}(\text{CH}_3\text{COO})_6]\), the term \(\mu\)-oxo refers to an oxygen atom (\(\text{O}\)) acting as a bridging ligand connecting the four beryllium atoms. This central oxygen forms an important part of the structure because it influences the geometry and bonding within the compound. The presence of \(\mu\) notation in a compound's name indicates the bridging nature of specific ligands, such as the oxo group in this case.

Polynuclear Complexes

Polynuclear complexes are coordination compounds that contain more than one metal atom in their structure. These complexes can display unique properties due to the interactions between the metal centers mediated by bridging ligands.

In the given compound \([\text{Be}_4 \text{O}(\text{CH}_3\text{COO})_6]\), it is a polynuclear complex consisting of four beryllium atoms. The oxo ligand bridges all of these metal atoms together, forming a tetrahedral array. This shared connectivity often stabilizes the entire structure and influences its chemical behavior.

Naming these complexes correctly involves considering the number of metal atoms (tetraberyllium in this case) and the types and roles of ligands, as indicated by terms like hexakis in the name.