Chemistry - Coordination Chemistry Question with Solution | TestHub

(a) ${\mathrm{Mn}}^{+}=3d^{5}4s^1$ In presence of $\mathrm{CO}$ effective configuration $=3d^{6}4s^0,3$ lone pair for back bonding with vacant orbital of $\mathrm{C}$ in $\mathrm{CO}$. (b) ${\mathrm{Fe}}^{\circ }=3d^{6}4s^2$ in presence of $\mathrm{CO}$ effective configuration $=3d^8,4$ lone pair for back bonding with $\mathrm{CO}$. (c) ${\mathrm{Cr}}^{\circ }=3d^{5}4s^1$, effective configuration $=3d^6$ 3 lone pair for back bonding with $\mathrm{CO}$. (d) ${\mathrm{V}}^{-}=3d^4{s}^2$, effective configuration $=3d^6,3$ lone pair for back bonding with $\mathrm{CO}$. Maximum back bonding in $\mathrm{Fe}(\mathrm{CO}{)}_5$, therefore $\mathrm{CO}$ bond order is lowest here.