`IUPAC` name for `[Fe(CO)_(2)(sigma-C_(5)H_(5))(pi -C_(5)H_(5))]` complex :

Options

A. Dicarbony1 (`eta^(5)`-cyclopentadieny1)(cyclopentadieny1) ferrate(II)
B. Dicarbony1 (`eta^(5)`-cyclopentadieny1)(cyclopentadieny1) iron(II)
C. Dicarbony1 (`eta^(5)`-cyclopentadieny1)(cyclopentadieny1) iron(II)
D. Dicarbony1 (`eta^(5)`-cyclopentadieny1)(cyclopentadieny1) iron(II)

Answer

To determine the IUPAC name for the complex \([Fe(CO)_{2}(\sigma-C_{5}H_{5})(\pi-C_{5}H_{5})]\), we will follow these steps:

### Step 1: Identify the Ligands
The complex contains two types of ligands:
- **Carbonyl (CO)**: There are two carbonyl groups.
- **Cyclopentadienyl (C₅H₅)**: This ligand is present in two forms: one is a sigma-bonded ligand (σ-C₅H₅) and the other is a pi-bonded ligand (π-C₅H₅).

### Step 2: Determine the Charge on the Metal
In this complex, iron (Fe) is the central metal atom. The carbonyl ligands are neutral, and the cyclopentadienyl ligands carry a charge of -1 each. Since there are two cyclopentadienyl ligands, their total charge is -2. To balance this, iron must have a charge of +2.

### Step 3: Name the Ligands
- The carbonyl ligands are named first. Since there are two carbonyl groups, we use the prefix "dicarbonyl".
- The cyclopentadienyl ligands are named next. The sigma-bonded cyclopentadienyl is named as "cyclopentadienyl" and the pi-bonded cyclopentadienyl is denoted using the prefix "eta" (η). Since it is a η⁵ complex (as it coordinates through all five carbons), we write it as "η⁵-cyclopentadienyl".

### Step 4: Assemble the Name
According to IUPAC naming conventions, we list the ligands in alphabetical order, ignoring any prefixes that indicate the number of ligands. Thus, we have:
1. Dicarbonyl
2. η⁵-cyclopentadienyl

Finally, we include the name of the metal with its oxidation state. Since iron has a +2 charge, we write it as "iron(II)".

### Final Name
Putting it all together, the IUPAC name for the complex \([Fe(CO)_{2}(\sigma-C_{5}H_{5})(\pi-C_{5}H_{5})]\) is:
**Dicarbonyl η⁵-cyclopentadienyl iron(II)**.