Question

Bonding in metal carbonyls is represented by the end structures.
`overset(M-C-=O" "harr" "M=C=O)(I" "II)`
The contribution of I and II to the real structure depends upon the extent of `pi-` back bonding. Both `sigma` donation and `pi-` back bonding are synergitc. The filled orbitals CO overlap with vacant metal d orbitals which is called `sigma` donation. The filled metal d orbitals overlap with `pi` antibondig moleculat orbital of CO. which is called `pi-`back bonding .
Which one of the following has the highest C-O bond length?
A. `[Ti (CO)_(6)]^(2-)`
B. `[V(CO)_(6)]^(-)`
C. `[Mn(CO)_(5)]^(+)`
D. `Cr(CO)_(6)`

Answer 1

Correct Answer - c
Note positive charge on the complex . Due to less electron density over the metal , less electrons are given into the `pi^(**)` MO of CO.