The correct IUPAC name of the following compound is `[Cr(NH_(3))_(5)(NCS)][ZnCl_(4)]`

Options

A. pentaammineisothiocyanatochromium(III) tetrachlorozincate(II)
B. pentammineisothiocyanatezinc chloridechromate(III)
C. pentaamineisothiocyanatochromate(II)
D. isothiocyanatopentaamminechromium(II) zinc chloride (IV).

Answer

To determine the correct IUPAC name of the compound `[Cr(NH₃)₅(NCS)][ZnCl₄]`, we can follow these steps:

### Step 1: Identify the Components of the Coordination Compound
The compound consists of two parts:
1. The cationic complex: `[Cr(NH₃)₅(NCS)]`
2. The anionic complex: `[ZnCl₄]`

### Step 2: Determine the Oxidation States
- **For Chromium (Cr)**:
Let the oxidation state of Cr be \( x \).
- Ammonia (NH₃) is a neutral ligand, contributing 0 to the charge.
- Thiocyanate (NCS) has a charge of -1.

The overall charge of the cationic complex is +2 (as it balances the -2 charge from the anionic complex).

The equation becomes:
\[ x + 5(0) + (-1) = +2 \]
Simplifying gives:
\[ x - 1 = 2 \implies x = +3 \]

- **For Zinc (Zn)**:
Let the oxidation state of Zn be \( y \).
- Each chloride (Cl) has a charge of -1, and there are 4 of them.

The overall charge of the anionic complex is -2.

The equation becomes:
\[ y + 4(-1) = -2 \]
Simplifying gives:
\[ y - 4 = -2 \implies y = +2 \]

### Step 3: Naming the Ligands
- **Ammonia (NH₃)** is named as **amine**.
- **Thiocyanate (NCS)** is named as **isothiocyanate**.
- **Chloride (Cl)** is named as **chloro**.

### Step 4: Construct the Name for the Cationic Complex
The cationic complex is `[Cr(NH₃)₅(NCS)]`:
- The name will be constructed as follows:
- Number of ligands: 5 amine ligands → **pentamine**
- 1 isothiocyanate ligand → **isothiocyanate**
- Metal: Chromium with oxidation state +3 → **chromium(III)**

Thus, the name of the cationic complex is **pentamine isothiocyanato chromium(III)**.

### Step 5: Construct the Name for the Anionic Complex
The anionic complex is `[ZnCl₄]`:
- The name will be constructed as follows:
- 4 chloride ligands → **tetrachloro**
- Metal: Zinc with oxidation state +2 → **zinc(II)**

Since it is an anionic complex, we use the suffix **-ate** for the metal:
Thus, the name of the anionic complex is **tetrachlorozincate(II)**.

### Step 6: Combine the Names
Now, we combine the names of both complexes:
- Cationic complex: **pentamine isothiocyanato chromium(III)**
- Anionic complex: **tetrachlorozincate(II)**

### Final IUPAC Name
The final IUPAC name of the compound is:
**pentamine isothiocyanato chromium(III) tetrachlorozincate(II)**.