Which from following complexes does NOT obey EAN rule?

Step-by-step solution

Effective Atomic Number analysis determines which complex violates the noble gas electron count rule. The EAN equals the sum of metal valence electrons and ligand-donated electrons, aiming for Kr (36), Xe (54), or Rn (86). For monodentate ligands: EAN = Z_ metal - oxidation state + 2 number of ligands . For Co ( NH ₃)₆³⁺ : Co atomic number 27, oxidation state +3 gives 24 valence electrons; 6 NH ₃ donate 12 electrons. EAN = 24 + 12 = 36 , satisfying the rule. For Cr ( CO )₆ : Cr atomic number 24, oxidation state 0 g