d
\(\begin{gathered}+2 \\ \text { (A) } \mathrm{K}_2\left[\mathrm{Ni}(\mathrm{CN})_4\right] \\ \mathrm{Ni}^{2+}:[\mathrm{Ar}] 3 \mathrm{~d}^8 4 \mathrm{~s}^{\circ},\left(\mathrm{CN}^{-} \text {is S.F.L) }\right. \\ \text { Pre hybridization state of } \mathrm{Ni}^{+2}\end{gathered}\)

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(B) \(\left[\mathrm{Ni}(\mathrm{CO})_4\right]\)

\(\mathrm{Ni}:[\mathrm{Ar}] 3 \mathrm{~d}^8 4 \mathrm{~s}^2\)

\(CO\) is \(S.F.L,\) so pairing occur

Pre hybridization state of \(\mathrm{Ni}\)

\(Image\)

\(\begin{aligned} & \text { (C) }\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_3 \\ & \mathrm{Co}^{+3}:[\mathrm{Ar}] 3 \mathrm{~d}^6 4 \mathrm{~s}^0 \\ & \text { With } \mathrm{Co}^{3+}, \mathrm{NH}_3 \text { act as S.F.L }\end{aligned}\)

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\(\begin{aligned} & \text { (d) } \mathrm{Na}_3\left[\mathrm{CoF}_6\right] \\ & \mathrm{Co}^{3+}:[\mathrm{Ar}] 3 \mathrm{~d}^6\left(\mathrm{~F}^{\Theta}: \text { W.F.L }\right)\end{aligned}\)

\(Image\)