Assertion: Zero and negative oxidation state of d-block metal ion are not possible in their complex compound.
Reason: Low oxidation state of the metal ions are found when a complex compound has ligands capable of `pi-`aceptor character in addition to the `sigma-` bonding.

Options

A. If both assertion and reason are true and the reason is the correct explanation of assertion
B. If both assertion and reason are true and the reason is not the correct explanation of assertion
C. If assertion is false but reason is true
D. If assertion is true but the reason is false

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that zero and negative oxidation states of d-block metal ions are not possible in their complex compounds.
- Generally, d-block metals can exhibit a variety of oxidation states, including zero and negative states, especially in coordination complexes.

2. **Analyzing the Reason**:
- The reason provided states that low oxidation states of metal ions are found when a complex compound has ligands capable of pi-acceptor character in addition to sigma bonding.
- Pi-acceptor ligands, such as carbonyl (CO) and phosphines (PR3), can stabilize low oxidation states of d-block metals through synergic bonding.

3. **Evaluating the Assertion**:
- The assertion is incorrect because d-block metals can indeed exhibit zero and negative oxidation states in certain complexes, particularly when coordinated with ligands that have pi-acceptor capabilities.

4. **Evaluating the Reason**:
- The reason is correct as it explains that the presence of pi-acceptor ligands allows for the stabilization of low oxidation states in d-block metal complexes.

5. **Conclusion**:
- Since the assertion is false and the reason is true, the correct relationship is that the assertion is not supported by the reason.

### Final Answer:
The assertion is false, and the reason is true.

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