Question

Transition metal complex with highest value of crystal field splitting \((Δ_0)\) will be

• A. \([Cr(H_2O)_6]3^+\)
• B. \([Mo(H_2O)_6]3^+\)
• C. \([Fe(H_2O)_6]3^+\)
• D. \([Os(H_2O)_6]3^+\)

Answer 1

The Correct Option is D

The question asks us to determine which transition metal complex has the highest value of crystal field splitting, denoted as \(Δ_0\). Let's analyze the options to understand which complex has the higher \(Δ_0\) value.

Crystal field splitting, \(Δ_0\), is dependent on several factors, including:

• The charge on the metal ion: Higher positive charge generally leads to larger splitting.
• The position of the metal in the periodic table: Usually, the 4d and 5d transition series have larger values of \(Δ_0\) compared to the 3d series because their electrons are more diffusely distributed, resulting in stronger interactions with ligands.
• The nature of the ligands: However, since all the complexes have the same ligand (\(H_2O\)), we focus on the metal ions.

Given the options:

1. \([Cr(H_2O)_6]^{3+}\): Chromium is from the 3d series.
2. \([Mo(H_2O)_6]^{3+}\): Molybdenum is from the 4d series.
3. \([Fe(H_2O)_6]^{3+}\): Iron is from the 3d series.
4. \([Os(H_2O)_6]^{3+}\): Osmium is from the 5d series.

From the metal ions presented:

• \(Cr^{3+}\) and \(Fe^{3+}\) are from the 3d transition series, which typically show lower crystal field splitting compared to their 4d and 5d counterparts.
• \(Mo^{3+}\) is from the 4d series and will have a moderate crystal field splitting.
• \(Os^{3+}\) is from the 5d series. The 5d elements experience the most significant crystal field splitting due to higher effective nuclear charge and better orbital overlap.

Therefore, the complex \([Os(H_2O)_6]^{3+}\) will have the largest crystal field splitting among the given options due to the reasons cited for 5d series metals and osmium being a heavier element with a significant positive charge.

Conclusion: The transition metal complex with the highest value of \(Δ_0\) is \([Os(H_2O)_6]3^+\).