Problem 7
Question
The complex that can show fac-and \(m e r\) - isomers is: (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right]^{+}\) (b) \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right]\) (c) \(\left[\mathrm{CoCl}_{2}(\mathrm{en})_{2}\right]\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3}\left(\mathrm{NO}_{2}\right)_{3}\right]\)
Step-by-Step Solution
Verified Answer
(d) \([\text{Co(NH}_3)_3(\text{NO}_2)_3]\) can show fac and mer isomers.
1Step 1: Understand the fac and mer isomers
The terms fac (facial) and mer (meridional) isomers refer to different geometric arrangements in octahedral complexes. A fac-isomer has three identical ligands on one face of the octahedron, forming a triangle, whereas a mer-isomer has three identical ligands arranged around the meridian, creating an L-shape.
2Step 2: Identify octahedral complexes with three identical ligands
For a complex to show fac-mer isomerism, it should have an octahedral geometry with three identical ligands. Check each given complex for these conditions: (a) \([\text{Co(NH}_3)_4\text{Cl}_2]^+\), (b) \([\text{Pt(NH}_3)_2\text{Cl}_2]\), (c) \([\text{CoCl}_2(\text{en})_2]\), and (d) \([\text{Co(NH}_3)_3(\text{NO}_2)_3]\).
3Step 3: Analyze each complex
- **Option (a)** is a coordination complex with six ligands overall, but has four ammonia and two chlorides. This cannot form fac-mer isomers.
- **Option (b)** is a square planar complex with four ligands, not suitable for fac-mer isomerism.
- **Option (c)** is also a coordination complex having ethylenediamine (en) ligands which are bidentate, preventing fac-mer isomerism.
- **Option (d)** is an octahedral complex with three identical nitrite (NO2) ligands, which can display both fac and mer isomerism.
4Step 4: Conclusion based on analysis
The only complex with a ligand arrangement that allows for both fac and mer isomerism is \([\text{Co(NH}_3)_3(\text{NO}_2)_3]\). This complex has three nitrite ligands that can form both fac and mer arrangements in an octahedral geometry.
Key Concepts
Facial and Meridional IsomerismOctahedral ComplexesGeometric Isomerism
Facial and Meridional Isomerism
In coordination chemistry, facial (fac) and meridional (mer) isomerism refers to the geometric arrangement of identical ligands within an octahedral complex. These isomers arise from different orientations of three identical ligands.
A fac-isomer is characterized by the positioning of three identical ligands on one face of an octahedron. Visualize it like a triangular face on a three-dimensional shape. All three ligands are adjacent to each other, forming a triangle when viewed from the top.
On the other hand, a mer-isomer has these ligands spread out around the meridian, a line that divides the octahedron. Imagine an L-shape or a dispersed arrangement rather than a compact triangle. Here, no two of the ligands are directly adjacent in a sequence.
Both arrangements are unique and can occur if the complex has exactly three identical ligands along with the octahedral geometry. Recognizing the difference between these isomers helps in understanding molecular geometry and properties.
A fac-isomer is characterized by the positioning of three identical ligands on one face of an octahedron. Visualize it like a triangular face on a three-dimensional shape. All three ligands are adjacent to each other, forming a triangle when viewed from the top.
On the other hand, a mer-isomer has these ligands spread out around the meridian, a line that divides the octahedron. Imagine an L-shape or a dispersed arrangement rather than a compact triangle. Here, no two of the ligands are directly adjacent in a sequence.
Both arrangements are unique and can occur if the complex has exactly three identical ligands along with the octahedral geometry. Recognizing the difference between these isomers helps in understanding molecular geometry and properties.
Octahedral Complexes
Octahedral complexes are a common structure in coordination compounds. They consist of a central metal atom surrounded by six ligands forming an octahedron. This geometric shape resembles two pyramids joined at their bases. It is essential because it accommodates six ligands symmetrically.
The arrangement of ligands in an octahedral complex is crucial for determining its isomeric possibilities. This includes not only facial and meridional isomerism but also other forms of isomerism.
Octahedral geometry is favored by metals with a coordination number of six and can have diverse types of ligands, leading to various chemical and physical properties based on the ligands' nature. Often, the study of octahedral complexes involves exploring these isomeric forms to understand reactivity, color, and ligand exchange processes.
Understanding octahedral complexes goes a long way in coordination chemistry, especially when analyzing transition metal compounds.
The arrangement of ligands in an octahedral complex is crucial for determining its isomeric possibilities. This includes not only facial and meridional isomerism but also other forms of isomerism.
Octahedral geometry is favored by metals with a coordination number of six and can have diverse types of ligands, leading to various chemical and physical properties based on the ligands' nature. Often, the study of octahedral complexes involves exploring these isomeric forms to understand reactivity, color, and ligand exchange processes.
Understanding octahedral complexes goes a long way in coordination chemistry, especially when analyzing transition metal compounds.
Geometric Isomerism
Geometric isomerism is a type of stereoisomerism where the spatial arrangement of ligands causes different properties. In coordination compounds, this is especially relevant in octahedral complexes with varied ligand groups.
For example, in structures with formula \([MA_3B_3]\), different isomers can form based on how the \(A\) and \(B\) ligands are positioned around the central metal. If all \(A\) or all \(B\) ligands occupy a single triangular face, it forms a fac-isomer. Conversely, if they are positioned alternatively along the meridian, it results in a mer-isomer.
Unlike structural isomers, which have different atomic connectivities, geometric isomers share the same connectivities but differ in the spatial arrangement of their atoms or groups. This leads to unique chemical behaviors, such as variations in stability, solubility, and optical activity.
Understanding geometric isomerism is vital for predicting how a compound might interact in different chemical environments, impacting its practical applications.
For example, in structures with formula \([MA_3B_3]\), different isomers can form based on how the \(A\) and \(B\) ligands are positioned around the central metal. If all \(A\) or all \(B\) ligands occupy a single triangular face, it forms a fac-isomer. Conversely, if they are positioned alternatively along the meridian, it results in a mer-isomer.
Unlike structural isomers, which have different atomic connectivities, geometric isomers share the same connectivities but differ in the spatial arrangement of their atoms or groups. This leads to unique chemical behaviors, such as variations in stability, solubility, and optical activity.
Understanding geometric isomerism is vital for predicting how a compound might interact in different chemical environments, impacting its practical applications.
Other exercises in this chapter
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