Identify the homoleptic complex(es) that is/are low spin. $$(A)[Fe(CN)_{5}NO]^{2-}(B)[CoF_{6}]^{3-}(C)[Fe(CN)_{6}]^{4-}(D)[Co(NH_{3})_{6}]^{3+}(E)[Cr(H_{2}O)_{6}]^{2+}$$ Choose the correct answer from the options given below :

We need to identify homoleptic complexes that are low spin from the given list.

(A) $$[Fe(CN)_5NO]^{2-}$$: Contains CN⁻ and NO — heteroleptic. Eliminated.

(B) $$[CoF_6]^{3-}$$: All F⁻ ligands — homoleptic.

(C) $$[Fe(CN)_6]^{4-}$$: All CN⁻ ligands — homoleptic.

(D) $$[Co(NH_3)_6]^{3+}$$: All NH₃ ligands — homoleptic.

(E) $$[Cr(H_2O)_6]^{2+}$$: All H₂O ligands — homoleptic.

(B) $$[CoF_6]^{3-}$$: Co³⁺ is $$d^6$$, F⁻ is a weak field ligand → high spin. Eliminated.

(C) $$[Fe(CN)_6]^{4-}$$: Fe²⁺ is $$d^6$$, CN⁻ is a strong field ligand → low spin. ✓

(D) $$[Co(NH_3)_6]^{3+}$$: Co³⁺ is $$d^6$$, NH₃ is a moderately strong field ligand, and Co³⁺ has high charge density → low spin. ✓

(E) $$[Cr(H_2O)_6]^{2+}$$: Cr²⁺ is $$d^4$$, H₂O is a weak field ligand → high spin. Eliminated.

The homoleptic and low spin complexes are (C) and (D).

The answer is Option B: (C) and (D) only.