Which of the following is correct ?

Options

A. Valence bond theory explains the colour of the coordination compounds .
B. `[NiCl_(4)]^(2-)` is diamagnetic in nature
C. Ambident ligands can show linkage isomerism .
D. A bidentate ligand can have four coordination sites .

Answer

To solve the question, we need to analyze the statements provided and determine which one is correct. Let's break down the statements one by one.

### Step-by-Step Solution:

1. **Statement A: Valence bond theory explains the color of coordination compounds.**
- Valence Bond Theory (VBT) does not directly explain the color of coordination compounds. The color is primarily due to the presence of unpaired electrons in the d-orbitals of the metal ion. If there are unpaired electrons, the compound will be colored. Therefore, this statement is **incorrect**.

2. **Statement B: NiCl4^2- is diamagnetic.**
- To analyze this, we need to determine the oxidation state of nickel in NiCl4^2-. Nickel in this complex has an oxidation state of +2. The electronic configuration of Ni in its elemental form is [Ar] 3d^8 4s^2. Upon losing two electrons (to form Ni^2+), the configuration becomes 3d^8.
- Chlorine is a weak field ligand and does not cause pairing of electrons. Therefore, the 3d^8 configuration will have unpaired electrons. Specifically, there will be 2 unpaired electrons in the 3d orbitals, making NiCl4^2- **paramagnetic**, not diamagnetic. Thus, this statement is **incorrect**.

3. **Statement C: Ambident ligands can show linkage isomerism.**
- This statement is correct. Ambident ligands have more than one atom that can coordinate to the metal center. For example, thiocyanate (SCN^-) can bind through either sulfur or nitrogen, leading to different isomers. Therefore, this statement is **correct**.

4. **Statement D: A bidentate ligand can have four coordination sites.**
- This statement is incorrect. A bidentate ligand can only coordinate through two donor atoms to the metal center. Thus, it cannot have four coordination sites. Therefore, this statement is **incorrect**.

### Conclusion:
The only correct statement among the options is **Statement C**: "Ambident ligands can show linkage isomerism."

### Final Answer:
The correct option is **C**.

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