The pair(s) of complexes wherein both exhibit tetrahedral geometry is(are) (Note: py = pyridine Given: Atomic numbers of Fe, Co, Ni and Cu are 26, 27, 28 and 29, respectively)

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Valence Bond Theory or VBT

Crystal Field Theory and Valence Bond Theory

Question

The pair(s) of complexes wherein both exhibit tetrahedral geometry is(are)

(Note: py = pyridine Given: Atomic numbers of Fe, Co, Ni and Cu are 26, 27, 28 and 29, respectively)

[Co(CO)₄]^– and [CoCl₄]^2–

[Ni(CO)₄] and [Ni(CN)₄]^2–

[Cu(py)₄]⁺ and [Cu(CN)₄]^3–

[FeCl₄]^– and [Fe(CO)₄]^2–

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(A) [FeCl₄]^–

Fe → [Ar] 3d⁶ 4s²

Fe⁺³ → [Ar] 3d⁵ 4s⁰

Cl^– is W.F.L. and does not pair up the unpaired electron of central metal atom.

[Fe(CO)₄]^2–

Fe → [Ar] 3d⁶ 4s²

Fe^2– → [Ar] 3d⁸ 4s²

(B) [Co(CO)₄]^–

Co → [Ar] 3d⁷ 4s²

Co^–1 → [Ar] 3d⁸ 4s²

[Co(CO)₄]^2–

Co → [Ar] 3d⁷ 4s²

Co⁺² → [Ar] 3d⁷ 4s⁰

Cl^– is W.F.L. and does not pair up the unpaired electron of central metal atom.

Ni → [Ar] 3d⁸ 4s²

Ni⁰ → [Ar] 3d⁸ 4s²

[Ni(CN)₄]^2–

Ni → [Ar] 3d⁸ 4s²

Ni⁺² → [Ar] 3d⁸ 4s⁰

CN^– is S.F.L. and pair up the unpaired electron of central metal atom.

(D) [Cu(py)₄]⁺

Cu → [Ar] 3d¹⁰ 4s¹

Cu⁺¹ → [Ar] 3d¹⁰ 4s⁰

[Cu(CN)₄]^3–

Cu → [Ar] 3d¹⁰ 4s¹

Cu⁺¹ → [Ar] 3d¹⁰ 4s⁰

CN^– is S.F.L. and pair up the unpaired electron of central metal atom.