Question

Which of the following is the correct order of increasing field strength of ligands to form coordination compounds ?

• A. \(SCN^{-} < F^{-} < C_2{O_4}^{2-} < CN^-\)
• B. \(SCN^{-} < F^{-} < CN^-< C_2{O_4}^{2-}\)
• C. \(SCN^{-} < F^{-} < CN^-< C_2{O_4}^{2-}\)\(\)
• D. \( CN^-< C_2{O_4}^{2-}<SCN^{-} < F^{-} \)\(\)

Answer 1

The Correct Option is A

The question asks for the correct order of increasing field strength of ligands to form coordination compounds. To answer this question, we need to refer to the spectrochemical series, which is an empirically derived list that ranks ligands based on their ability to split the d orbitals of a metal ion and is a measure of ligand field strength.

The spectrochemical series in terms of increasing field strength is approximately:

• \(I^{-} \lt Br^{-} \lt SCN^{-} \lt Cl^{-} \lt F^{-} \lt OH^{-} \lt C_2O_4^{2-} \lt H_2O \lt NH_3 \lt en \lt bipy \lt phen \lt NO_2^{-} \lt PPh_3 \lt CN^{-} \lt CO\)

Examining our options:

• \(SCN^{-}\) is a weak field ligand, weaker than \(F^{-}\).
• \(F^{-}\) is weaker than \(C_2O_4^{2-}\) (oxalate).
• \(C_2O_4^{2-}\) is weaker than \(CN^{-}\).

Thus, the correct order from weakest to strongest ligand based on field strength is:

• \(SCN^{-} \lt F^{-} \lt C_2O_4^{2-} \lt CN^{-}\)

This matches with option \(SCN^{-} \lt F^{-} \lt C_2O_4^{2-} \lt CN^{-}\), which is the correct answer.