Which of the following has longest C-O bond length? (free C-O bond length in CO is 1.128 A0)
-
[Co(CO)4]-
-
[Fe(CO)4]-2
-
[Mn(CO)6]+
-
Ni(CO)4
B.
[Fe(CO)4]-2
As the negative charge on metal carbonyl complex increases back pi bonding increases and hence the bond length of C-O bond increases while the bond length of metal-carbon bond decreases. Hence,[Fe(CO)4]2- has longest C-O bond length among the given complexes.
The correct order of bond length of the given complexes is
[Mn(CO)6]+<[Ni(CO)4]<[Co(CO)4]-<[Fe(CO)4]2-