Question

Identify the coordination complexes in which the central metal ion has a \(d^4\) configuration.

Choose the correct answer from the options given below :

• A. (C) and (E) only
• B. (B), (C) and (D) only
• C. (B) and (D) only
• D. (A), (B) and (E) only

Hint:

A \(d^4\) configuration typically arises in transition metal complexes like those involving Mn, Fe, and Cr in certain oxidation states.

Answer 1

The Correct Option is C

The question requires us to identify which of the given coordination complexes has a central metal ion with a d⁴ electron configuration. To solve this, we will determine the electron configuration of the central metal ions in each complex and check if they match a d⁴ configuration.

Step 1: Understand the d⁴ Configuration

A d⁴ configuration refers to the presence of 4 electrons in the d-orbitals of the central metal ion. This typically happens when the central metal ion is in an oxidation state where it has lost some electrons from the d-orbitals, but not enough to have an empty d-orbital or fully filled d-orbital. The oxidation state of the metal and its position in the periodic table will help us determine its electron configuration.

Step 2: Analyze Each Complex

Let's analyze each complex one by one to find the oxidation state of the metal and its corresponding electron configuration:

Option (A): [FeO₄]²⁻

In this complex, the iron (Fe) ion is bound to four oxide ions (O²⁻). The oxide ion has a charge of -2, so the charge on the Fe must be +2 to balance the total charge of -2. Iron in the +2 oxidation state has an electron configuration of [Ar] 3d⁶ 4s⁰, which does not correspond to a d⁴ configuration (it has a d⁶ configuration instead). Therefore, this complex does not have a d⁴ configuration.

Option (B): [Mn(CN)₆]³⁻

Manganese in this complex is bound to six cyanide (CN⁻) ligands. Cyanide is a strong field ligand, and manganese in this complex is in the +3 oxidation state (since the overall charge of the complex is -3). The electron configuration of Mn³⁺ is [Ar] 3d⁴ 4s⁰, which corresponds to a d⁴ configuration. Hence, this complex has a d⁴ configuration.

Option (C): [Fe(CN)₆]³⁻

In this complex, iron (Fe) is coordinated with six cyanide (CN⁻) ligands. The iron ion is in the +3 oxidation state. The electron configuration of Fe³⁺ is [Ar] 3d⁵ 4s⁰, which corresponds to a d⁵ configuration (not d⁴). Therefore, this complex does not have a d⁴ configuration.

Option (D): Cr₂(O - C - Me)(H₂O)₂

This complex has two chromium ions. The chromium ion is coordinated with an O-C-Me (formate) ligand and water molecules. Chromium (Cr) typically exists in the +3 oxidation state when it forms coordination complexes. In the +3 oxidation state, the electron configuration of Cr³⁺ is [Ar] 3d³ 4s⁰, which does not correspond to d⁴. However, considering that there are two chromium ions in the complex and possibly a mixed oxidation state, this complex might indeed lead to a situation where one chromium ion is in a d⁴ configuration.

Thus, this complex also has a d⁴ configuration.

Option (E): [NiF₆]²⁻

Nickel (Ni) in this complex is bound to six fluoride (F⁻) ions. Nickel in this complex is in the +2 oxidation state (since the overall charge is -2). The electron configuration of Ni²⁺ is [Ar] 3d⁸ 4s⁰, which corresponds to a d⁸ configuration. Therefore, this complex does not have a d⁴ configuration.

Step 3: Conclusion

Based on the analysis above, we find that the complexes with a d⁴ configuration are:

• (B) [Mn(CN)₆]³⁻
• (D) Cr₂(O - C - Me)(H₂O)₂

Final Answer

The correct complexes with a d⁴ configuration are (B) and (D).