The IR stretchin frequencies of free CO, and CO in [V(CO)6]-, [Cr(CO)6] and [Mn(CO)6]+ are 2143 cm^- — Coordination Compounds Chemistry Question

💡 Solution & Explanation

Step 1: In an octahedral field, the five d-orbitals split into lower t_2g and higher e_g energy levels. Step 2: For d^1, d^2, and d^3 configurations, electrons fill the three t_2g orbitals singly according to Hund's rule regardless of field strength. Step 3: Therefore, the number of unpaired electrons in a d^3 system is always fixed at 3, making option (a) the correct answer.