According to IUPAC system, the name of the complex, `[Co(en)_2Cl(ONO)]^(+)` is :

Options

A. Chloronitrodi(ethylenediamine)cobalt(III) ion
B. Chloridobis(ethylenediamine) nitrito-O-cobalt(III) ion
C. Chlorobis(ethylenediamine)nitrocobalt (III) ion
D. Nitrochlorobis (ethylenediamine)cobalt(III) ion

Explanation

To name the complex ion \([Co(en)_2Cl(ONO)]^+\) according to the IUPAC nomenclature system, follow these steps:

### Step-by-Step Solution:

1. **Identify the Ligands**:
- The ligands present in the complex are:
- Ethylene diamine (en) - a neutral bidentate ligand.
- Chloride (Cl) - a monodentate ligand with a negative charge.
- Nitrito (ONO) - a monodentate ligand that can be named as nitrito-O when it binds through the oxygen atom.

2. **Count the Number of Each Ligand**:
- There are two ethylene diamine ligands, one chloride ligand, and one nitrito ligand.

3. **Name the Ligands in Alphabetical Order**:
- According to IUPAC rules, ligands are named in alphabetical order regardless of their charge or number.
- The ligands in alphabetical order are:
- Chlorido (for Cl)
- Bis(ethylene diamine) (for two en ligands)
- Nitrito (for ONO)

4. **Combine the Ligand Names**:
- The combined name of the ligands is:
- Chlorido, bis(ethylene diamine), nitrito

5. **Name the Central Metal**:
- The central metal in this complex is cobalt (Co).
- Determine the oxidation state of cobalt.
- Let the oxidation state of cobalt be \(x\).
- Ethylene diamine is neutral (0), chloride contributes -1, and nitrito contributes -1.
- The overall charge of the complex is +1.
- Therefore, the equation is:
\[ x + 0 - 1 - 1 = +1 \implies x - 2 = 1 \implies x = +3 \]
- Thus, cobalt is in the +3 oxidation state.

6. **Combine the Names**:
- The full name of the complex is:
- Chlorido bis(ethylene diamine) nitrito cobalt(III)

### Final Answer:
The name of the complex \([Co(en)_2Cl(ONO)]^+\) is **Chlorido bis(ethylene diamine) nitrito cobalt(III)**.