IUPAC name `[Co(NH_(3))_(5)(NO_(2))]Cl_(2)` is

Options

A. Nitrito-N-pentaamminecobalt(III)chloride
B. Nitrito-N-pentaamminecobalt(II) chloride
C. Pentaamminenitrito-N-cobalt(II)chloride
D. Pentaamminenitrito-N-cobalt (III) chloride

Answer

To derive the IUPAC name of the complex `[Co(NH₃)₅(NO₂)]Cl₂`, we will follow a systematic approach:

### Step 1: Determine the oxidation state of the central metal atom (Cobalt, Co)
Let the oxidation state of Co be \( x \).

- NH₃ is a neutral ligand, contributing 0 to the oxidation state.
- NO₂ is a negative ligand (specifically nitrito), contributing -1 to the oxidation state.
- Cl is a negatively charged ligand as well, and since there are 2 Cl ions, it contributes -2 to the oxidation state.

The overall charge of the complex is neutral (0). Therefore, we can set up the equation:

\[ x + 0 + (-1) + (-2) = 0 \]

This simplifies to:

\[ x - 3 = 0 \implies x = +3 \]

### Step 2: Identify the ligands and their names
- The ligands present are:
- 5 NH₃ ligands, which are called "ammine".
- 1 NO₂ ligand, which is called "nitrito" when it is bonded through the nitrogen atom.

### Step 3: Arrange the ligands in alphabetical order
When naming the ligands, we must consider their alphabetical order:
- "ammine" (A) comes before "nitrito" (N).

### Step 4: Write the name of the complex
Based on the number of each type of ligand:
- 5 NH₃ ligands = pentaammine
- 1 NO₂ ligand = nitrito

Thus, we write the name of the complex as:

\[ \text{pentaammine nitrito} \]

### Step 5: Name the central metal and its oxidation state
The central metal is cobalt, and since we determined its oxidation state to be +3, we denote this in Roman numerals as (III).

### Step 6: Combine all parts to form the complete name
Putting it all together, we have:

\[ \text{pentaammine nitrito} \text{cobalt(III)} \text{chloride} \]

Since there are 2 chloride ions outside the coordination sphere, we write:

\[ \text{pentaammine nitrito cobalt(III) chloride} \text{ (2)} \]

### Final IUPAC Name
The final IUPAC name of the complex `[Co(NH₃)₅(NO₂)]Cl₂` is:

\[ \text{pentaammine nitrito cobalt(III) chloride} \]