Chemistry - Coordination Chemistry Question with Solution | TestHub

The M-C $\pi$-bond character (back-bonding) increases with higher electron density on the metal. As the negative charge on the metal carbonyl increases, the metal's electron density increases, enhancing back-bonding. Thus, the order is ${\left[\mathrm{Mn}(\mathrm{CO}{)}_6\right]}^{+}<\left[\mathrm{Cr}(\mathrm{CO}{)}_6\right]<{\left[\mathrm{V}(\mathrm{CO}{)}_6\right]}^{-}$.