Match List-I (Complex) with List-II (Hybridisation & Magnetic characters): (A) [MnBr4]2-, (B) [FeF6]3-, (C)…

🧠 Match Each Complex to Its (Hybridisation, Spin) Pair

Identify metal d-config, geometry, ligand field, and resulting hybridisation for each.

🗺️ Evaluate Each

| Complex | Metal/d-config | Geometry | Ligand field | Hybridisation | Magnetism | |---|---|---|---|---|---| | (A) $[\mathrm{MnBr_4}]^{2-}$ | Mn(II) d⁵ | Td (Br⁻ weak) | weak HS | $sp^3$ | paramagnetic (5 unpaired) | | (B) $[\mathrm{FeF_6}]^{3-}$ | Fe(III) d⁵ | Octahedral | F⁻ weak → HS | $sp^3 d^2$ | paramagnetic (5 unpaired) | | (C) $[\mathrm{Co(C_2O_4)_3}]^{3-}$ | Co(III) d⁶ | Octahedral | ox moderate-strong → LS | $d^2 sp^3$ | diamagnetic | | (D) $[\mathrm{Ni(CO)_4}]$ | Ni(0) d¹⁰ | Td (CO strong forces sp³) | strong | $sp^3$ | diamagnetic |

🗺️ Match to List-II

| Complex | Result | Match (List-II) | |---|---|---| | (A) $[\mathrm{MnBr_4}]^{2-}$ | $sp^3$ + paramagnetic | (IV) | | (B) $[\mathrm{FeF_6}]^{3-}$ | $sp^3 d^2$ + paramagnetic | (II) | | (C) $[\mathrm{Co(C_2O_4)_3}]^{3-}$ | $d^2 sp^3$ + diamagnetic | (I) | | (D) $[\mathrm{Ni(CO)_4}]$ | $sp^3$ + diamagnetic | (III) |

So: (A)-(IV), (B)-(II), (C)-(I), (D)-(III).

⚡ Tetrahedral $sp^3$ Magnetism

Td $sp^3$ complexes can be:

• d⁰ or d¹⁰ (diamagnetic): Ni(CO)₄, [Zn(NH₃)₄]²⁺.
• Mid d-config (paramagnetic, HS): [MnBr₄]²⁻, [CoCl₄]²⁻, [NiCl₄]²⁻.

⚠️ Oxalate Forces LS Co(III)

Oxalate (ox) is moderately strong; combined with Co(III)'s already-high $\Delta_o$, Co(III) almost always goes LS d⁶ → diamagnetic.

$\boxed{\text{Answer: (4) (A)-(IV), (B)-(II), (C)-(I), (D)-(III)}}$