Match the complexes given in List-I with oxidation state and the type…

The correct answer is Option (2) → (A) (IV), (B)-(III), (C)-(II), (D)-(I)

List-I Complex	List-II Oxidation state and type of complex
(A) $[Co(NH_3)_6]^{3+}$	(IV) +3 and Inner orbital complex
(B) $[COF_6]^{3-}$	(III) +3 and Outer orbital complex
(C) $[NiCl_4]^{2-}$	(II) +2 and Outer orbital complex
(D) $[Ni(CN)_4]^{2-}$	(I) +2 and Inner orbital complex

(A) [Co(NH₃)₆]³⁺

• Co has a +3 oxidation state (since 6 NH₃ ligands are neutral).
• NH₃ is a strong field ligand → causes low-spin (inner orbital) complex.
   So, Oxidation state +3, Inner orbital complex → IV

(B) [CoF₆]³⁻

• Co must be +3 (because 6 F⁻ ligands, each −1 → total −6 charge, complex charge is −3 → Co = +3).
• F⁻ is a weak field ligand → high-spin, outer orbital complex.
   So, Oxidation state +3, Outer orbital complex → III

(C) [NiCl₄]²⁻

• Ni must be +2 (Cl⁻ is −1, 4 Cl⁻ → −4, complex charge −2 → Ni = +2).
• Cl⁻ is a weak field ligand → outer orbital, high-spin complex.
   So, +2, Outer orbital complex → II

(D) [Ni(CN)₄]²⁻

• Ni is +2 (CN⁻ is −1, 4 CN⁻ → −4, complex charge −2 → Ni = +2).
• CN⁻ is a strong field ligand → low-spin, inner orbital complex.
   So, +2, Inner orbital complex → I