Q54 / 120 · NEET 2012 (Mains) · Chemistry

Low spin complex of $d^6$-cation in an octahedral field will have the following energy $\left(\Delta_o=\right.$ crystal field splitting energy in an octahedral field, $P=$ electron pairing energy)

  • A
    $\frac{-12}{5} \Delta_o+P$
  • Correct answer
    B
    $\frac{-12}{5} \Delta_o+3 P$
  • C
    $\frac{-2}{5} \Delta_o+2 P$
  • D
    $\frac{-2}{5} \Delta_o+P$

Solution

\(\text {C.F.S.E. }=(-0.4 x+0.6 y) \Delta_o+z P\) where \(\mathrm{x}=\) number of electrons occupying \(\mathrm{t}_{2 g}\) orbital \(y=\) number of electrons occupying \(e_g\) orbital \(z=\) number of pairs of electrons For low spin \(\mathrm{d}^6\) complex electronic configuration \(\begin{aligned} & =t_{2 g}^6 e_g^0 \text { or } t_{2 g}^{2,2,2} e_g^0 \\ & \therefore \quad x=6, y=0, z=3 \\ & \text { C.F.S.E. }=(-0.4 \times 6+0 \times 0.6) \Delta_o+3 P \\ & =\frac{-12}{5} \Delta_o+3 P \end{aligned}\)

Hence, the correct answer is option: 'B'.

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