In complex hydrides, hydride ions act as ligand and are coordinated to metal ions. These hydrides are good reducing agents. Which of the following hydrides is not a complex hydride ?

Options

A. `LiAIH_(4)`
B. `NaBH_(4)`
C. `(AIH_(3))_(n)`
D. `LiBH_(4)`

Explanation

To determine which of the given hydrides is not a complex hydride, we need to analyze each option based on the definition of complex hydrides. Complex hydrides are compounds where hydride ions (H⁻) act as ligands and are coordinated to a central metal atom.

Let's go through the options step by step:

1. **Option A: LiAlH₄ (Lithium Aluminum Hydride)**
- This compound consists of aluminum (Al) as the central metal atom coordinated by four hydride ions (H⁻).
- The structure can be represented as AlH₄⁻, where Al is surrounded by four H⁻ ions.
- Since H⁻ acts as a ligand here, LiAlH₄ is a complex hydride.

2. **Option B: NaBH₄ (Sodium Borohydride)**
- In this case, boron (B) is the central metal atom coordinated by four hydride ions (H⁻).
- The structure can be represented as BH₄⁻, where B is surrounded by four H⁻ ions.
- As H⁻ acts as a ligand, NaBH₄ is also a complex hydride.

3. **Option C: Metal Hydride (e.g., MH)**
- This option refers to a general metal hydride where the metal (M) is bonded to hydrogen atoms.
- In polymeric hydrides, when n (the number of hydrogen atoms) is less than or equal to 4, the structure does not involve coordination of H⁻ as ligands but rather simple bonding.
- Therefore, this type of hydride does not qualify as a complex hydride.

4. **Option D: LiBH₄ (Lithium Borohydride)**
- Similar to NaBH₄, lithium borohydride also has boron (B) as the central atom coordinated by four hydride ions (H⁻).
- Thus, LiBH₄ is a complex hydride.

After analyzing all options, we can conclude that **Option C (Metal Hydride)** is not a complex hydride.

### Final Answer:
**C. Metal Hydride (e.g., MH)** is not a complex hydride.