Question

Which of the following has the lowest 'C-O' bond strength?

• A. $\left[Cr\right(CO{)}_6]$
• B. $\left[Ti\right(CO{)}_6{]}^{2-}$
• C. $\left[Mn\right(CO{)}_6{]}^{+}$
• D. $\left[V\right(CO{)}_6{]}^{-}$

Answer 1

The correct option is B $\left[Ti\right(CO{)}_6{]}^{2-}$

We know,
More the extent of back bonding, higher will be the bond order of $M-C$ and lower will be the bond order of $C-O$.

High bond order will have higher bond strength.

Among the isoelectronic species, $Ti$ has the lowest oxidation state so it has highest tendency to donate electron pair to the carbonyl compare to others. So, $Ti-C$ bond strength increases and the bond order of 'C-O' decreases. Hence, it will have the lowest bond strength.

Hence, option (d) is correct.