NEET2026ChemistryChapterActual
Identify the set of coordination complexes in which all the species are diamagnetic in nature.
Options
- A[ Fe ( CN )₆ ]⁴⁻, [ Co ( NH ₃ )₆ ]³⁺, [ PtCl ₄ ]²⁻
- B[ Fe ( CN )₆ ]³⁻, [ Co ( en )₃ ]³⁺, [ Cu ( NH ₃ )₄ ]²⁺
- C[ CoF ₆ ]³⁻, [ Mn ( CN )₆ ]³⁻, [ Cr ( NH ₃ )₆ ]³⁺
- D[ Fe ( H ₂ O )₆ ]²⁺, [ Co ( C ₂ O ₄ )₃ ]³⁻, [ MnCl ₄ ]²⁻
Correct answer
A. [ Fe ( CN )₆ ]⁴⁻, [ Co ( NH ₃ )₆ ]³⁺, [ PtCl ₄ ]²⁻
Step-by-step solution
In [ Fe ( CN )₆ ]⁴⁻ , Fe is in +2 oxidation state with a 3d^6 configuration. Since CN ^- is a strong field ligand, electrons pair up to give t_ 2g ^6 e_g^0 . It has zero unpaired electrons and is diamagnetic. In [ Co ( NH ₃ )₆ ]³⁺ , Co is in +3 oxidation state with a 3d^6 configuration. NH ₃ acts as a strong field ligand for Co ³⁺ , leading to t_ 2g ^6 e_g^0 . It has zero unpaired electrons and is diamagnetic. In [ PtCl ₄ ]²⁻ , Pt is in +2 oxidation state with a 5d^8 configuration. For 4d and 5d series metals, the