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: Understanding the Concept:
This question requires knowledge of the IUPAC nomenclature rules for coordination compounds. We need to identify the ligands, the central metal atom, and the overall charge of the complex to determine the correct name.
Step 2: Key Formula or Approach:
The IUPAC naming rules for coordination compounds are as follows:
1. Ligands: Name the ligands first in alphabetical order. Use prefixes (di, tri, tetra, etc.) to indicate the number of each type of ligand.
2. Central Metal: Name the central metal atom or ion.
- If the complex is a cation or is neutral, the metal is given its usual name (e.g., iron, copper, cobalt).
- If the complex is an anion, the metal's name ends in "-ate" (e.g., ferrate, cuprate, cobaltate).
3. Oxidation State: The oxidation state of the central metal is written in Roman numerals in parentheses immediately after the metal's name.
Step 3: Detailed Explanation:
Let's apply these rules to [Fe(CO)\(_5\)].
1. Ligand Identification: The ligand is CO, which is named "carbonyl". There are five CO ligands, so we use the prefix "penta-". The name of the ligand part is "pentacarbonyl".
2. Central Metal and Complex Charge: The central metal is Fe (Iron). The carbonyl ligand (CO) is a neutral molecule (charge = 0). Since there are no other ions or charges indicated, the overall charge of the complex is 0. The complex is neutral.
3. Oxidation State of Fe: Let the oxidation state of Fe be x.
\[ x + 5 \times (\text{charge of CO}) = \text{overall charge} \] \[ x + 5 \times (0) = 0 \] \[ x = 0 \] The oxidation state of iron is 0.
4. Assembling the Name:
- Since the complex is neutral, we use the regular name for the metal: "iron".
- The ligand part is "pentacarbonyl".
- The oxidation state is (0).
Putting it all together, the name is Pentacarbonyliron(0).
Let's analyze the options:
(A) and (B) and (E) use "ferrate", which is incorrect for a neutral complex.
(D) gives the incorrect oxidation state (II).
(C) matches our derived name perfectly.
Step 4: Final Answer:
The IUPAC name of [Fe(CO)\(_5\)] is Pentacarbonyliron(0). This corresponds to option (C).