Consider the following complexes:
(i) `[FeIF(CN)(H_(2)O)(en)]`
(ii) `[MoCl_(2)F_(2)(gly)]^(2-)`
Then, calculate value of `|x-y|` (where x and y are total number of possible optically active isomers in (i) and (ii) complex respectively).

Explanation

To solve the problem, we need to determine the number of optically active isomers for each of the given coordination complexes and then calculate the absolute difference between these numbers.

### Step 1: Analyze the first complex `[FeI(CN)(H2O)(en)]`

1. **Identify the ligands**: The ligands in this complex are Iodide (I), Cyanide (CN), Water (H2O), and Ethylenediamine (en). Ethylenediamine is a bidentate ligand, meaning it can attach to the metal at two points.

2. **Determine the coordination number**: Iron (Fe) typically has a coordination number of 6 in this type of complex.

3. **Count the possible isomers**:
- The complex can be arranged in different ways due to the presence of the bidentate ligand (en).
- The total number of isomers can be calculated using the formula for optical isomers, which is based on the arrangement of ligands around the central metal ion.
- For this complex, we can find that there are **12 possible optical isomers**.

### Step 2: Analyze the second complex `[MoCl2F2(gly)]^(2-)`

1. **Identify the ligands**: The ligands in this complex are Chloride (Cl), Fluoride (F), and Glycine (gly). Glycine is also a bidentate ligand.

2. **Determine the coordination number**: Molybdenum (Mo) also has a coordination number of 6 in this complex.

3. **Count the possible isomers**:
- Similar to the first complex, we need to consider the arrangement of the ligands.
- The presence of two types of monodentate ligands (Cl and F) and one bidentate ligand (gly) leads to different arrangements.
- After analyzing the possible arrangements, we find that there are **4 possible optical isomers**.

### Step 3: Calculate the absolute difference

- Let \( x \) be the number of optically active isomers for the first complex, which is 12.
- Let \( y \) be the number of optically active isomers for the second complex, which is 4.
- We need to calculate \( |x - y| \).

\[ |x - y| = |12 - 4| = |8| = 8 \]

### Final Answer
The value of \( |x - y| \) is **8**.

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