In which of the following complexes the valence shell of central metal ion does not have `d^(6)` electronic configuration?

Options

A. `[Fe(H_(2)O)_(6)]^(2+)`
B. `[Mn(H_(2)O)]^(2+)`
C. `[Co(H_(2)O)]^(3+)`
D. `[Ni(H_(2)O)]^(4+)`

Explanation

To determine which of the given complexes does not have a central metal ion with a `d^(6)` electronic configuration, we will analyze each complex step by step.

### Step 1: Identify the central metal ion and its oxidation state for each complex.
1. **Complex 1: [Fe(H2O)6]²⁺**
- Oxidation state of Fe: Let the oxidation state be \( x \).
- The water molecules (H2O) are neutral, so:
\[
x + 0 = +2 \implies x = +2
...