Which of the following carbonyls will have the strongest $\mathrm{C}-\mathrm{O}$ bond?
Which of the following carbonyls will have the strongest $\mathrm{C}-\mathrm{O}$ bond?
$\operatorname{Mn}(\mathrm{CO})_6^{+}$
$\mathrm{Cr}(\mathrm{CO})_6$
$\mathrm{V}(\mathrm{CO})_6^{-}$
$\mathrm{Fe}(\mathrm{CO})_5$
Solution
As positive charge on the central metal atom increases, the less readily the metal can donate electron density into the anti bonding $\pi$-orbitals of CO ligand to weaken the $\mathrm{C}-\mathrm{O}$ bond. Hence, the $\mathrm{C}-\mathrm{O}$ bond would be strongest in $\mathrm{Mn}(\mathrm{CO})_6^{+}$.