What are Ambidentate Ligands?
Ambidentate ligands are ligands that have two different donor atoms through which they can coordinate with the central metal ion, but they coordinate through only one donor atom at a time.
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Two possible donor atoms
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Coordinates through only one at a time
1. Nitrite Ion (NO₂⁻)
Nitrite ion can coordinate through either the nitrogen atom or an oxygen atom.
Nitro: M–NO₂ (through N)
Nitrito: M–ONO (through O)
2. Thiocyanate Ion (SCN⁻)
SCN⁻ can coordinate through either sulfur or nitrogen.
Thiocyanato-S: M–SCN
Thiocyanato-N: M–NCS
SCN⁻ → S or N donor
Linkage isomerism is a type of structural isomerism shown by coordination compounds containing an ambidentate ligand.
It occurs when the same ligand coordinates with the central metal ion through different donor atoms.
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Different donor atom
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Different coordination compound
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Linkage Isomerism
A common example involves the ambidentate nitrite ion, NO₂⁻.
Nitro Complex
Co–N bond
Here, the nitrite ligand coordinates through its nitrogen atom. This form is called the nitro form.
Nitrito Complex
Co–O bond
Here, the same nitrite ligand coordinates through its oxygen atom. This form is called the nitrito form.
Nitro ⇄ Nitrito
Linkage Isomerism
The thiocyanate ion, SCN⁻, is also an ambidentate ligand. It can coordinate through S or N.
Through Sulphur
Thiocyanato-S
Through Nitrogen
Thiocyanato-N
| Point | Ambidentate Ligand | Linkage Isomerism |
|---|---|---|
| Meaning | Ligand having two possible donor atoms | Isomerism due to different donor atoms |
| Cause | Presence of two donor atoms | Different coordination through those donor atoms |
| Example | NO₂⁻, SCN⁻ | Nitro–Nitrito complexes |
- Ambidentate ligands have two different donor atoms.
- They coordinate through only one donor atom at a time.
- NO₂⁻ can coordinate through N or O.
- SCN⁻ can coordinate through S or N.
- Linkage isomerism is a type of structural isomerism.
- It occurs because an ambidentate ligand can attach to the metal through different donor atoms.
- NO₂⁻ through N gives the nitro form.
- NO₂⁻ through O gives the nitrito form.
- SCN⁻ through S gives thiocyanato-S.
- SCN⁻ through N gives thiocyanato-N.
Q. Define an ambidentate ligand. Give one example.
Answer:
An ambidentate ligand is a ligand having two different donor atoms through which it can coordinate with the central metal ion, but it coordinates through only one donor atom at a time.
Example: NO₂⁻ can coordinate through N or O.
Q. What is linkage isomerism? Explain with an example.
Linkage isomerism occurs in coordination compounds containing ambidentate ligands. It arises when the same ligand coordinates with the central metal through different donor atoms.
For NO₂⁻:
Nitro form – Co–N
[Co(NH₃)₅(ONO)]Cl₂
Nitrito form – Co–O
These are linkage isomers.
Q. Explain ambidentate ligands and linkage isomerism with suitable examples.
Ambidentate Ligands
Ligands having two different donor atoms capable of coordinating with a metal ion through either one of them are called ambidentate ligands.
Examples include NO₂⁻ and SCN⁻.
Linkage Isomerism
When an ambidentate ligand coordinates through different donor atoms, the resulting coordination compounds are called linkage isomers.
The first is the nitro form and the second is the nitrito form.
Q. Explain linkage isomerism in coordination compounds with suitable examples.
Linkage isomerism is a type of structural isomerism found in coordination compounds containing ambidentate ligands.
An ambidentate ligand contains two possible donor atoms but coordinates through only one of them at a time.
Example 1 – NO₂⁻
Nitro – Co–N
Nitrito – Co–O
Example 2 – SCN⁻
M–NCS → Through N
Q. Define ambidentate ligands. Explain linkage isomerism in detail with suitable examples.
1. Definition of Ambidentate Ligand
An ambidentate ligand is a ligand which contains two different donor atoms and can coordinate with a central metal ion through either one of them, but not both simultaneously at the same coordination site.
2. Examples
SCN⁻ → S or N donor
3. Linkage Isomerism
Linkage isomerism is a type of structural isomerism in which the same ambidentate ligand is attached to the central metal ion through different donor atoms.
4. Nitro–Nitrito Example
Nitro form
Co–N bond
Nitrito form
Co–O bond
Both compounds have the same molecular formula but differ in the atom of NO₂⁻ through which coordination occurs.
5. Thiocyanate Example
Thiocyanato-S
Thiocyanato-N
6. Conclusion
1. An ambidentate ligand contains:
✅ Answer
B
2. Which is an ambidentate ligand?
✅ Answer
C) NO₂⁻
3. NO₂⁻ can coordinate through:
✅ Answer
C) N or O
4. SCN⁻ can coordinate through:
✅ Answer
A) S or N
5. Linkage isomerism is associated with:
✅ Answer
B
6. Linkage isomerism is a type of:
✅ Answer
A
7. Coordination through nitrogen of NO₂⁻ gives:
✅ Answer
B) Nitro
8. Coordination through oxygen of NO₂⁻ gives:
✅ Answer
B) Nitrito
9. The donor atom in the nitro form is:
✅ Answer
B) Nitrogen
10. The donor atom in the nitrito form is:
✅ Answer
B) Oxygen
11. Which pair represents linkage isomers?
✅ Answer
B
12. In thiocyanato-S linkage, the metal is bonded through:
✅ Answer
B) S
13. In thiocyanato-N linkage, the metal is bonded through:
✅ Answer
B) N
14. Which ligand is NOT ambidentate?
✅ Answer
C) NH₃
15. In linkage isomerism, the molecular formula is:
✅ Answer
B) Same
16. Linkage isomerism arises due to difference in:
✅ Answer
B
17. Which ligand can show nitro-nitrito linkage?
✅ Answer
C) NO₂⁻
18. Which of the following has S and N as possible donor atoms?
✅ Answer
B) SCN⁻
19. Which statement is correct about ambidentate ligands?
✅ Answer
B
20. The correct sequence is:
✅ Answer
A
🎯 Quick Revision
NO₂⁻: N or O donor
SCN⁻: S or N donor
Linkage Isomerism: Same ligand attaches through different donor atoms
Nitro: Co–N–O₂
Nitrito: Co–O–N=O
Important Example: [Co(NH₃)₅(NO₂)]Cl₂ ⇄ [Co(NH₃)₅(ONO)]Cl₂
