IUPAC name of `[Co(NH_3)_5NO_2]Cl_2`

Options

A. (a) pentamminentro-N-cobalt (III) chloride
B. (b) pentaamminenitrosocobalt (III) chloride
C. (c) pentaamminenitrocobalt (II) chloride
D. (d) None of these

Explanation

To determine the IUPAC name of the coordination compound \([Co(NH_3)_5NO_2]Cl_2\), we will follow a systematic approach.

### Step-by-Step Solution:

1. **Identify the Coordination Complex**:
The given compound is \([Co(NH_3)_5NO_2]Cl_2\). Here, \([Co(NH_3)_5NO_2]^2+\) is the cationic part and \(Cl^-\) is the anionic part.

2. **Identify the Ligands**:
The ligands in the complex are:
- \(NH_3\) (Ammonia), which is a neutral ligand and is named "ammine".
- \(NO_2\) (Nitrite), which is named "nitro" when it acts as a ligand.

3. **Count the Number of Each Ligand**:
- There are five \(NH_3\) ligands, so we use the prefix "penta".
- There is one \(NO_2\) ligand, so we simply use "nitro".

4. **Write the Ligands in Alphabetical Order**:
When naming ligands, we arrange them in alphabetical order based on their names (ignoring any prefixes).
- "ammine" comes before "nitro", so we write "pentaammine" first followed by "nitro".

5. **Name the Central Metal**:
The central metal is cobalt (Co). We need to determine its oxidation state.

6. **Determine the Oxidation State of Cobalt**:
- The overall charge of the complex ion is \(+2\) (since there are two chloride ions, each with a \(-1\) charge).
- The ammonia ligands are neutral, and the nitro ligand contributes \(-1\) (as it is acting as a nitro ligand).
- Let the oxidation state of cobalt be \(x\). The equation is:
\[ x + 5(0) + (-1) = +2 \implies x - 1 = 2 \implies x = +3 \]
Thus, cobalt has an oxidation state of \(+3\).

7. **Combine the Names**:
Now we can combine the names of the ligands and the metal with its oxidation state:
- The name of the complex cation is "pentaammine nitro cobalt(III)".

8. **Name the Anion**:
The anion is \(Cl^-\), which is named "chloride".

9. **Final IUPAC Name**:
Combine the names of the cation and anion:
- The complete IUPAC name of the compound is "pentaammine nitro cobalt(III) chloride".

### Final Answer:
**IUPAC Name**: pentaammine nitro cobalt(III) chloride