Which of the following is not a metal carbonyl?

Options

A. `Ni(CO)_4`
B. `[Co(CN)_6]^(3-)`
C. `Mn_2(CO)_10`
D. `Fe(CO)_5`

Answer

To determine which of the following is not a metal carbonyl, we need to understand what constitutes a metal carbonyl. A metal carbonyl is a coordination compound that contains carbon monoxide (CO) as a ligand bonded to a transition metal.

### Step-by-Step Solution:

1. **Identify Metal Carbonyls**: Recall that metal carbonyls are coordination complexes that include carbon monoxide as a ligand. The general formula for a metal carbonyl can be represented as [M(CO)n], where M is a metal and n is the number of CO ligands attached to it.

2. **List the Given Options**: Although the specific options are not provided in the question, we will assume there are several compounds listed (let's say A, B, C, D).

3. **Analyze Each Option**:
- **Option A**: Check if it contains CO as a ligand. If it does, it is a metal carbonyl.
- **Option B**: Again, check for the presence of CO. If it contains CO, it is a metal carbonyl.
- **Option C**: Repeat the same check. If CO is present, it is a metal carbonyl.
- **Option D**: Check if it contains any other ligand instead of CO (like CN, for example). If it does not contain CO, then it is not a metal carbonyl.

4. **Conclusion**: After analyzing all options, the compound that does not contain carbon monoxide as a ligand is identified as the one that is not a metal carbonyl.

5. **Final Answer**: Based on the analysis, the answer is the compound that contains a ligand other than CO, which we can denote as D in our example.