In complex compounds, metal ligand bond is

Options

A. Coordinate bond
B. Hydrogen bond
C. Ionic bond
D. Covalent bond

Explanation

To answer the question: "In complex compounds, metal-ligand bond is...", we need to analyze the nature of the bond formed between the metal ion and the ligands in coordination compounds.

### Step-by-Step Solution:

1. **Understanding Coordination Compounds**:
- Coordination compounds consist of a central metal atom or ion bonded to surrounding ligands. Ligands are ions or molecules that can donate a pair of electrons to the metal.

2. **Identifying the Type of Bond**:
- The bond formed between the metal and the ligand is known as a coordinate bond (also called a dative bond). In this type of bond, both electrons in the bond originate from the ligand.

3. **Example of a Coordination Compound**:
- Consider the example of the complex ion [FeCl4]²⁻. Here, iron (Fe) is the central metal atom, and it is surrounded by four chloride ions (Cl⁻) acting as ligands.

4. **Formation of the Coordinate Bond**:
- Each chloride ion donates a pair of electrons to the iron ion, forming a coordinate bond. This is distinct from ionic or covalent bonds, where the electron sharing or transfer is different.

5. **Conclusion**:
- Therefore, in complex compounds, the metal-ligand bond is specifically a coordinate bond.

### Final Answer:
In complex compounds, the metal-ligand bond is a **coordinate bond**.

---