Question

The IUPAC name of $[\mathrm{Fe(CO)_5}]$ is:

• A. Pentacarbonylferrate(0)
• B. Pentacarbonylferrate(III)
• C. Pentacarbonyliron(0)
• D. Pentacarbonyl iron(II)
• E. Pentacarbonylferrate(II)

Hint:

For naming coordination compounds, first check whether the complex is neutral or anionic. Neutral complex uses the normal metal name, while anionic complex uses the “-ate” form.

Answer 1

The Correct Option is C

Step 1: Identify the ligands present in the complex.
The complex is \[ [\mathrm{Fe(CO)_5}] \] The ligand present is carbon monoxide, denoted by \( \mathrm{CO} \).
In coordination nomenclature, \( \mathrm{CO} \) is named as carbonyl.

Step 2: Count the number of ligands.
There are five carbonyl ligands attached to iron.
Therefore, the ligand part of the name becomes: \[ \text{pentacarbonyl} \]

Step 3: Determine whether the complex is neutral, cationic, or anionic.
The complex \[ [\mathrm{Fe(CO)_5}] \] has no overall charge shown, so it is a neutral complex.
For neutral complexes, the metal name is written in its normal form, so we use: \[ \text{iron} \] and not \[ \text{ferrate} \] because “ferrate” is used for anionic complexes.

Step 4: Determine the oxidation state of iron.
Each carbonyl ligand \( \mathrm{CO} \) is a neutral ligand.
Let the oxidation state of iron be \( x \).
Since the whole complex is neutral: \[ x + 5(0) = 0 \] \[ x = 0 \] So the oxidation state of iron is: \[ \mathrm{0} \]

Step 5: Write the full name in IUPAC style.
Thus, the name is: \[ \text{pentacarbonyliron(0)} \]

Step 6: Eliminate the incorrect options.
Options containing “ferrate” are incorrect because the complex is not anionic.
Options with oxidation states \( +2 \) or \( +3 \) are also incorrect because carbonyl is neutral and the complex has overall charge zero.

Step 7: Final conclusion.
Hence, the IUPAC name is \[ \boxed{\text{Pentacarbonyliron(0)}} \] Therefore, the correct option is \[ \boxed{(3)} \]