Question

Match the LIST-I with LIST-II

Choose the correct answer from the options given below:

• A. A-III, B-IV, C-II, D-I
• B. A-III, B-I, C-IV, D-II
• C. A-III, B-IV, C-I, D-II
• D. A-II, B-I, C-IV, D-III

Hint:

In a tetrahedral complex, use the formula CFSE = [-0.6(number of e electrons) + 0.4(number of t2 electrons)] $\Delta_t$.

Answer 1

The Correct Option is C

We can determine the Crystal Field Stabilization Energy (CFSE) for high-spin tetrahedral complexes by following the electron filling order into 'e' (lower energy) and '$t_2$' (higher energy) sets. The energy of an electron in 'e' is $-0.6\Delta_t$ and in '$t_2$' is $+0.4\Delta_t$.

Case A ($d^2$): Two electrons in 'e'. CFSE = $2 \times (-0.6) = -1.2 \Delta_t$. (Matches III)
Case B ($d^4$): Two electrons in 'e' and two in '$t_2$'. CFSE = $[2 \times (-0.6)] + [2 \times 0.4] = -1.2 + 0.8 = -0.4 \Delta_t$. (Matches IV)
Case C ($d^6$): One more electron in 'e' and one in '$t_2$' relative to $d^4$ (considering $d^5$ adds zero energy). Distribution is $e^3 t_2^3$. CFSE = $[3 \times (-0.6)] + [3 \times 0.4] = -1.8 + 1.2 = -0.6 \Delta_t$. (Matches I)
Case D ($d^8$): Four electrons in 'e' and four in '$t_2$'. CFSE = $[4 \times (-0.6)] + [4 \times 0.4] = -2.4 + 1.6 = -0.8 \Delta_t$. (Matches II)

By matching these calculated values with List-II, we obtain the sequence: A-III, B-IV, C-I, D-II, which corresponds to option 3.