Chemistry - Coordination Chemistry Question with Solution | TestHub

Neglecting pairing energy
I. $[\mathrm{Mn}(\mathrm{CN})\mathrm{B}{]}^{3-}\Rightarrow {\mathrm{Mn}}^{3+},{\mathrm{t}}_2{\mathrm{g}}^4,\mathrm{CFSE}=-0.4\times 4\Delta \mathrm{o}$ $=-1.6\Delta$ 。
II. $[\mathrm{Co}(\mathrm{CN})8{]}^{4-}\Rightarrow {\mathrm{Co}}^{2+},{\mathrm{t}}_2{}^6{\mathrm{eg}}^1,\mathrm{CFSE}=-0.4\times 6+$ $0.6\times 1=-1.8{\Delta }_{\circ }$
III. ${\left[\mathrm{Fe}(\mathrm{CN}{)}_8\right]}^{4-}\Rightarrow {\mathrm{Fe}}^{2+},{\mathrm{t}}_{2g}{}^6{\mathrm{e}}^0,\mathrm{CFSE}=-0.4\times 6=$ $-2.4{\Delta }_0$
IV. ${\left[\mathrm{Fe}(\mathrm{CN}{)}_8\right]}^{3-}\Rightarrow {\mathrm{Fe}}^{3+},{\mathrm{t}}_{2g}{}^5{\mathrm{e}}^0,\mathrm{CFSE}=-0.4\times 5=$ $-2{\Delta }_0$
Order of stability III $>$ IV $>$ II $>$ I