Which of the following complex show maximum paramagnetism ?

Options

A. `[Co(Ox)_2(NH_3)_2]^-`
B. `[Fe(en)(bipy)(NH_3)_2]^(2+)`
C. `[Pd(gly)(PPh_3)_2]^+`
D. `[Ti(H_2O)_6]^(3+)`

Answer

To determine which of the given complexes shows maximum paramagnetism, we need to analyze the oxidation states and the number of unpaired electrons in each complex. Paramagnetism is directly related to the presence of unpaired electrons; the more unpaired electrons, the greater the paramagnetism.

### Step-by-Step Solution:

1. **Identify the complexes and their ligands:**
- Complex 1: Cobalt with oxalate ion and NH3
- Complex 2: Iron with diethylene amine, bipyridine, and ammonia
- Complex 3: Palladium with glycine and triphenylphosphine
- Complex 4: Titanium with water

2. **Calculate the oxidation state of the central metal in each complex:**
- **Complex 1:**
- Cobalt (Co) with oxalate (C2O4^2-) and NH3
- Let the oxidation state of Co be x.
- Equation: x + 2(-2) + 0 = -1 (total charge)
- Solving gives x = +3.

- **Complex 2:**
- Iron (Fe) with diethylene amine, bipyridine, and ammonia
- Let the oxidation state of Fe be y.
- Equation: y + 0 + 0 + 0 = +2 (total charge)
- Solving gives y = +2.

- **Complex 3:**
- Palladium (Pd) with glycine and triphenylphosphine
- Let the oxidation state of Pd be z.
- Equation: z - 1 + 0 = 0 (total charge)
- Solving gives z = +1.

- **Complex 4:**
- Titanium (Ti) with water
- Let the oxidation state of Ti be w.
- Equation: w + 0 = +3 (total charge)
- Solving gives w = +3.

3. **Determine the electronic configuration of each metal in its oxidation state:**
- **Complex 1 (Co^3+):**
- Atomic number of Co = 27, configuration = [Ar] 3d^7 4s^2
- For Co^3+: 3d^6 (two electrons removed)
- Strong field ligands (oxalate and NH3) cause pairing: 0 unpaired electrons (diamagnetic).

- **Complex 2 (Fe^2+):**
- Atomic number of Fe = 26, configuration = [Ar] 3d^6 4s^2
- For Fe^2+: 3d^6 (two electrons removed)
- Strong field ligands cause pairing: 0 unpaired electrons (diamagnetic).

- **Complex 3 (Pd^2+):**
- Atomic number of Pd = 46, configuration = [Kr] 4d^10 5s^0
- For Pd^2+: 4d^8 (two electrons removed)
- Mixed field ligands (glycine is weak, triphenylphosphine is strong) cause some pairing: 0 unpaired electrons (diamagnetic).

- **Complex 4 (Ti^3+):**
- Atomic number of Ti = 22, configuration = [Ar] 3d^2 4s^2
- For Ti^3+: 3d^1 (three electrons removed)
- Weak field ligand (water) does not cause pairing: 1 unpaired electron (paramagnetic).

4. **Conclusion:**
- **Complex 1:** 0 unpaired electrons (diamagnetic)
- **Complex 2:** 0 unpaired electrons (diamagnetic)
- **Complex 3:** 0 unpaired electrons (diamagnetic)
- **Complex 4:** 1 unpaired electron (paramagnetic)

Thus, the complex that shows maximum paramagnetism is **Complex 4 (Titanium with water)**.