Which of the following has longest `C-O` bond length? (Free `C-O` bond length in CO is `1.128Å`).

Options

A. `Ni(CO)_4`
B. `[Co(CO)_4]^(-)`
C. `[Fe(CO)_4]^(2-)`
D. `[Mn(CO)_6]^(+)`

Answer

C

Explanation

`[Fe(CO)_4^(2-)`
Since metal atom is carrying maximum -ve charge therefore it would show maximum synergic bonding as a resultant C-O bond length would be maximum .