The correct IUPAC name of the complex `[Cr(NH_3)_5(NCS)][ZnCl_4]` is

Options

A. Pentaammine isothiocyanato chromium (III) tetrachloro zincate (II)
B. Pentaammine isothiocyanato chromium (IV) tetrachloro zincate (III)
C. Tetrachloro zincate (II) pentaammine isothiocyanato chromium (III)
D. Pentaammine tetrachloro zincate (II) isothiocyanato chromium (III)

Answer

To determine the correct IUPAC name of the complex \([Cr(NH_3)_5(NCS)][ZnCl_4]\), we will follow these steps:

### Step 1: Identify the components of the complex
The complex consists of two parts: a cation \([Cr(NH_3)_5(NCS)]^{3+}\) and an anion \([ZnCl_4]^{2-}\).

### Step 2: Determine the oxidation states
1. **For Chromium (Cr)**:
- Let the oxidation state of Cr be \(x\).
- Ammonia (\(NH_3\)) is a neutral ligand, contributing \(0\) to the charge.
- Isothiocyanate (\(NCS\)) has a charge of \(-1\).
- The total charge of the cation is \(+3\) (since it balances with the anion).
- The equation becomes:
\[ x + 5(0) + (-1) = +3 \implies x - 1 = 3 \implies x = +4 \]

2. **For Zinc (Zn)**:
- Let the oxidation state of Zn be \(y\).
- Each chloride (\(Cl\)) has a charge of \(-1\).
- The total charge of the anion is \(-2\).
- The equation becomes:
\[ y + 4(-1) = -2 \implies y - 4 = -2 \implies y = +2 \]

### Step 3: Naming the ligands
- The ligand \(NH_3\) is called "ammine".
- The ligand \(NCS\) is called "isothiocyanato" because it is bound through the nitrogen atom.

### Step 4: Constructing the name
1. **Cation**:
- The cation is named first. We have 5 ammine ligands, so we use the prefix "penta".
- The name of the cation will be "pentaammineisothiocyanatochromium(III)" because the oxidation state of chromium is \(+3\).

2. **Anion**:
- The anion is named next. We have 4 chloride ligands, so we use the prefix "tetra".
- The name of the anion will be "tetrachlorozinc(II)" because the oxidation state of zinc is \(+2\).

### Step 5: Final IUPAC Name
Putting it all together, the full name of the complex is:
\[ \text{pentaammineisothiocyanatochromium(III) tetrachlorozinc(II)} \]