Question

Which one of the following has largest number of isomers?

Options

• [Ru(NH₃)₄Cl₂]⁺

• [Co(NH₃)₅Cl]²⁺

• [Ir(PR₃)₂H(CO)]²⁺

• [Co(en)₂Cl₂]⁺

Answer 1

[Co(en)₂Cl₂]⁺

Explanation:

[Co(en)₂Cl₂]⁺ is an octahedral complex with two bidentate en ligands and two chloride ions; it exhibits cis–trans isomerism, and the cis form is optically active (Λ and Δ), giving a total of three isomers. In comparison, [Ru(NH₃)₄Cl₂]⁺ (MA₄B₂ type) shows only cis–trans isomerism, giving two isomers; [Co(NH₃)₅Cl]²⁺ (MA₅B type) has only one form; and [Ir(PR₃)₂H(CO)]²⁺ (square planar MA₂BC type) also shows cis–trans isomerism, giving two isomers.