In the complex `[CoCl_(2)(en)_(2)]Br`, the co-ordination number and oxidation state of cobalt are :

Options

A. 6 and +3
B. 3 and +3
C. 4 and +2
D. 6 and +1

Answer

To determine the coordination number and oxidation state of cobalt in the complex \([CoCl_2(en)_2]Br\), we can follow these steps:

### Step 1: Identify the Ligands
In the complex \([CoCl_2(en)_2]Br\), we have:
- Two chloride ions (\(Cl^-\))
- Two ethylenediamine (en) ligands

### Step 2: Determine the Coordination Number
The coordination number is defined as the total number of ligand donor atoms that are bonded to the central metal atom (cobalt in this case).

- Each \(Cl^-\) ligand contributes 1 to the coordination number.
- Ethylenediamine (en) is a bidentate ligand, which means it can bind through two donor atoms. Since there are two en ligands, they contribute \(2 \times 2 = 4\) to the coordination number.

Thus, the total coordination number is:
\[ \text{Coordination Number} = 2 \, (from \, Cl) + 4 \, (from \, en) = 6 \]

### Step 3: Determine the Oxidation State of Cobalt
Let the oxidation state of cobalt be \(x\). The overall charge of the complex is determined by the charges of the ligands and the counter ion (bromide ion, \(Br^-\)).

The charges are as follows:
- Each \(Cl^-\) contributes \(-1\) (2 \(Cl^-\) contribute \(-2\)).
- Ethylenediamine (en) is a neutral ligand, contributing \(0\).
- The \(Br^-\) ion contributes \(-1\).

The overall charge of the complex can be set up as:
\[ x + (-2) + 0 = +1 \]
This is because the \(Br^-\) ion outside the coordination sphere gives the entire complex a +1 charge.

Now, we can solve for \(x\):
\[ x - 2 = 1 \]
\[ x = 1 + 2 = 3 \]

### Conclusion
Thus, the oxidation state of cobalt in the complex \([CoCl_2(en)_2]Br\) is \(+3\) and the coordination number is \(6\).

### Final Answer
- Coordination Number: 6
- Oxidation State of Cobalt: +3