In complex compounds, the ligand `ONO^(-)` is named as:

Options

A. nitrato
B. nitrito
C. nitro
D. none of these.

Explanation

To determine the name of the ligand `ONO^(-)` in complex compounds, we will follow these steps:

### Step 1: Identify the Ligand
The ligand `ONO^(-)` is derived from the nitrite ion, which has the molecular formula `NO2^(-)`.

### Step 2: Understand the Naming Conventions
In coordination chemistry, ligands are named according to specific conventions. For anionic ligands, the naming often involves a suffix that indicates the type of ligand.

### Step 3: Determine the Correct Name
The ligand `ONO^(-)` can be named in two ways depending on its bonding:
- When it is bonded through the nitrogen atom, it is called "nitro".
- When it is bonded through the oxygen atom, it is called "nitrito".

In the case of `ONO^(-)`, it is typically referred to as "nitrito" when it is acting as a ligand in coordination compounds.

### Step 4: Finalize the Answer
Thus, the correct name for the ligand `ONO^(-)` in complex compounds is "nitrito".

### Conclusion
The answer to the question is **option B: nitrito**.

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