Question
Among the following metal carbonyls, the $$C - O$$ bond order is lowest in
A.
$${\left[ {Mn{{\left( {CO} \right)}_6}} \right]^ + }$$
B.
$$\left[ {Fe{{\left( {CO} \right)}_5}} \right]$$
C.
$$\left[ {Cr{{\left( {CO} \right)}_6}} \right]$$
D.
$${\left[ {V{{\left( {CO} \right)}_6}} \right]^ - }$$
Answer :
$${\left[ {V{{\left( {CO} \right)}_6}} \right]^ - }$$
Solution :
An anionic carbonyl complex can delocalise more electron density to antibonding $$pi$$ - orbital of $$CO$$ and hence, lowers the bond order.