Problem 119 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is/are correc regarding metal carbonyl? (a) In \(\mathrm{Fe}_{3}(\mathrm{CO})_{12}\) no. of \(\mathrm{Fe}-\mathrm{Fe}\) bonds are 3 (b) In \(\mathrm{Mn}_{2}(\mathrm{CO})_{10}\) bond order of \(\mathrm{Mn}-\mathrm{Mn}\) is 0 (c) \(\mathrm{Fe}(\mathrm{CO})\), is diamagnetic

Step-by-Step Solution

Answer

Statements (a) and (c) are correct; (b) is incorrect.

Step 1: Analyze Fe3(CO)12

First, consider the structure of \( \mathrm{Fe}_3(\mathrm{CO})_{12} \). This compound is known to have a metal cluster with 3 iron atoms. In such compounds, the iron atoms can form direct metal-metal bonds. For \( \mathrm{Fe}_3(\mathrm{CO})_{12} \), there are a total of 3 \( \mathrm{Fe}-\mathrm{Fe} \) bonds in its cluster structure.

Step 2: Evaluate Mn2(CO)10 for Bond Order

Next, let's consider \( \mathrm{Mn}_2(\mathrm{CO})_{10} \). To find the bond order between the manganese atoms, we consider the electronic configuration and molecular orbitals. The bond order is calculated using the formula: \( \text{Bond Order} = \frac{1}{2}(\text{Number of bonding electrons} - \text{Number of antibonding electrons}) \). In \( \mathrm{Mn}_2(\mathrm{CO})_{10} \), each manganese contributes 7 valence electrons, and the molecule has 78 valence electrons overall. After making CO bonding arrangements, the \( \mathrm{Mn} - \mathrm{Mn} \) bond is present with a bond order of 1.

Step 3: Check Magnetic Properties of Fe(CO)5

Finally, examine \( \mathrm{Fe(CO)}_5 \). In this compound, \( \mathrm{Fe} \) is in the zero oxidation state and has a configuration of \(3d^6 4s^0\). The strong field CO ligands cause pairing of electrons. Consequently, this makes \( \mathrm{Fe(CO)}_5 \) a diamagnetic compound, as all electrons are paired.

Key Concepts

Fe3(CO)12 structure

Fe3(CO)12 is a fascinating metal carbonyl compound due to its intricate structure. It is known for having a cluster of three iron atoms. These iron atoms form direct bonds with each other. So, in essence, there are three iron-iron (Fe-Fe) bonds. The arrangement of these bonds creates a structure where each iron atom is bonded to two other iron atoms, forming a triangular cluster. This structural arrangement allows the iron atoms to share electrons efficiently, stabilizing the overall molecule.

• The geometry allows for optimal overlap of the d orbitals from the iron atoms, which facilitates bond formation.
• The carbon monoxide (CO) ligands are bonded to the iron atoms, helping balance electron density.

Metal clustering is a prevalent feature in such complex compounds, lending to unique properties like catalysis and electron transfer abilities.

Mn2(CO)10 bond order

The metal carbonyl Mn2(CO)10 offers great insight into bond order concepts. Bond order is an important factor that gives information about the stability and strength of a bond. It is calculated using the formula: \[ \text{Bond Order} = \frac{1}{2}(\text{Number of bonding electrons} - \text{Number of antibonding electrons}) \]The manganese atoms in Mn2(CO)10 contribute 7 electrons each. With a total of 78 valence electrons, setting the stage for intricate bonding.

• Post CO ligand bonding and electron distribution, the Mn-Mn bond exhibits a bond order of 1.
• This indicates a single bond between the two manganese atoms.
• Such a bond order reflects moderate bond strength, balancing reactivity and stability.

Recognizing the bonding nature between manganese atoms is vital to understanding the reactivity and properties of Mn2(CO)10.

Fe(CO)5 magnetic properties

Fe(CO)5 is a metal carbonyl compound characterized by its magnetic properties, which stem from its unique electron configuration. The iron atom in Fe(CO)5 is in a zero oxidation state, utilizing an electronic configuration of 3d^6.

• CO ligands, being strong field ligands, cause the pairing of iron's electrons.
• This pairing results in all electrons being paired in Fe(CO)5.
• A compound where all electrons are paired is termed diamagnetic.

The lack of unpaired electrons ensures diamagnetism, meaning the compound will not be attracted to a magnetic field. Understanding these properties helps in appreciating the behavior of carbonyls in various physical and chemical processes.