Problem 119
Question
Which of the following statements is/are correct 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) \(\mathrm{Fe}(\mathrm{CO})_{5}\) is diamagnetic (d) In \(\mathrm{Fe}_{2}(\mathrm{CO})_{4}\) all bond length are same
Step-by-Step Solution
Verified Answer
A and C are correct.
1Step 1: Analyze Statement A
The compound \( \mathrm{Fe}_3(\mathrm{CO})_{12} \) can be represented as \( [\mathrm{Fe}(\mathrm{CO})_4]_3 \), which has a cluster structure allowing multiple \( \mathrm{Fe}-\mathrm{Fe} \) bonds. Each iron is bonded to two other iron atoms, forming a triangular cluster. This means that there are 3 \( \mathrm{Fe}-\mathrm{Fe} \) bonds in \( \mathrm{Fe}_3(\mathrm{CO})_{12} \).
2Step 2: Analyze Statement B
In \( \mathrm{Mn}_2(\mathrm{CO})_{10} \), two manganese atoms are directly bonded, but this bond is bridged by carbonyl groups. The bond order is generally calculated based on electron-sharing between the two atoms. \( \mathrm{Mn} \) in the zero oxidation state forms a bond order of 1 as the effective bond is reduced to it being mainly filled with bridge carbonyls rather than a direct \( \mathrm{Mn}-\mathrm{Mn} \). Hence, the bond order is not zero and is indeed \( 1 \). Statement B is incorrect.
3Step 3: Analyze Statement C
The compound \( \mathrm{Fe}(\mathrm{CO})_{5} \) is known to have all electrons paired. Iron in this complex has an electronic configuration of \( 3d^{10} \) due to back-bonding, and because of the absence of unpaired electrons, \( \mathrm{Fe}(\mathrm{CO})_{5} \) is indeed diamagnetic.
4Step 4: Analyze Statement D
The compound \( \mathrm{Fe}_2(\mathrm{CO})_4 \) does not exist in a viable and stable state, and presumably there is a different intended complex. If it is \( \mathrm{Fe}_2(\mathrm{CO})_9 \), this compound forms a \( \mathrm{Fe}-\mathrm{Fe} \) bond, resulting in variations in bond distances. So, assuming this misunderstanding, the statement would be incorrect because not all bond lengths would be the same.
Key Concepts
Bond OrderDiamagnetic ComplexesIron-Carbonyl ClustersCoordination Chemistry
Bond Order
Bond order is an important concept when discussing metal carbonyls. It indicates the number of shared electron pairs between two atoms.
In simple terms, a higher bond order means a stronger bond.
It is calculated as the difference between bonding and antibonding electrons, divided by two.
For example, in the compound \(\mathrm{Mn}_2(\mathrm{CO})_{10}\), the Mn-Mn bond is surrounded by carbonyl groups.
Although the direct bond might seem absent, the presence of bonding electrons via bridging carbonyl groups contributes to the bond order, making it 1 rather than 0.
Bond order helps explain the stability and strength of the bonds:
In simple terms, a higher bond order means a stronger bond.
It is calculated as the difference between bonding and antibonding electrons, divided by two.
For example, in the compound \(\mathrm{Mn}_2(\mathrm{CO})_{10}\), the Mn-Mn bond is surrounded by carbonyl groups.
Although the direct bond might seem absent, the presence of bonding electrons via bridging carbonyl groups contributes to the bond order, making it 1 rather than 0.
Bond order helps explain the stability and strength of the bonds:
- A bond order of 0 indicates no bond.
- A bond order of 1 suggests a single bond.
- Higher numbers represent stronger, multi-bonds.
Diamagnetic Complexes
Diamagnetic complexes are fascinating in coordination chemistry because they contain no unpaired electrons. This leads to their characteristic non-magnetic behavior.
In such complexes, all electrons are paired, which means the net magnetic moment is zero.
An excellent example of a diamagnetic complex is \(\mathrm{Fe}(\mathrm{CO})_{5}\).
Due to back-bonding from CO to Fe, iron achieves a filled electron configuration, making all electron spins paired.
This results in the compound being non-responsive to a magnetic field. Understanding whether a complex is diamagnetic is crucial for predicting its magnetic properties:
In such complexes, all electrons are paired, which means the net magnetic moment is zero.
An excellent example of a diamagnetic complex is \(\mathrm{Fe}(\mathrm{CO})_{5}\).
Due to back-bonding from CO to Fe, iron achieves a filled electron configuration, making all electron spins paired.
This results in the compound being non-responsive to a magnetic field. Understanding whether a complex is diamagnetic is crucial for predicting its magnetic properties:
- Diamagnetic complexes are repelled by magnetic fields.
- They typically have their most stable electronic configuration.
- Information about electron pairing aids in determining chemical reactivity.
Iron-Carbonyl Clusters
Iron-carbonyl clusters are a special category of metal carbonyls where iron atoms are bonded together by carbonyl groups.
These are characterized by their tendency to form clusters of iron atoms, such as \(\mathrm{Fe}_3(\mathrm{CO})_{12}\), forming a triangular array of iron atoms.
In this configuration, each iron atom is connected to two others via \(\mathrm{Fe}-\mathrm{Fe}\) bonds.
Such structures are fascinating for studying metal-metal bonding and electron delocalization.
Highlights of iron-carbonyl clusters include:
These are characterized by their tendency to form clusters of iron atoms, such as \(\mathrm{Fe}_3(\mathrm{CO})_{12}\), forming a triangular array of iron atoms.
In this configuration, each iron atom is connected to two others via \(\mathrm{Fe}-\mathrm{Fe}\) bonds.
Such structures are fascinating for studying metal-metal bonding and electron delocalization.
Highlights of iron-carbonyl clusters include:
- The close proximity of metal atoms allows for significant electron sharing.
- They exhibit unique stability due to their cluster formation and delocalization.
- This architecture aids in exploring theoretical concepts in coordination chemistry.
Coordination Chemistry
Coordination chemistry explores the interactions between metal ions and ligands, such as carbonyl groups.
It is central to understanding the structure, bonding, and reactivity of complexes, like metal carbonyls.
In coordination chemistry, ligands can be mono-dentate, bi-dentate, or polydentate, based on their bonding sites.
Coordination number refers to how many ligands are attached to the central metal atom.
For example, \(\mathrm{Fe}(\mathrm{CO})_{5}\) is a coordination complex with a coordination number of 5 due to the five carbonyl groups attached to the iron atom.
It is central to understanding the structure, bonding, and reactivity of complexes, like metal carbonyls.
In coordination chemistry, ligands can be mono-dentate, bi-dentate, or polydentate, based on their bonding sites.
Coordination number refers to how many ligands are attached to the central metal atom.
For example, \(\mathrm{Fe}(\mathrm{CO})_{5}\) is a coordination complex with a coordination number of 5 due to the five carbonyl groups attached to the iron atom.
- Explore how ligands affect the geometry and properties of a complex.
- Understand the role of ligand types and bonding strength.
- Predict reactivity patterns based on electron configuration.
Other exercises in this chapter
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