Coordination Compounds - Result Question 75
####82. Which of the following has longest $C-O$ bond length? (Free $C-O$ bond length in $CO$ is $1.128 \AA$ )
[2016]
(a) $[Ni(CO)_4]$
(b) $[Co(CO)_4]$
(c) $[Fe(CO)_4]^{2-}$
(d) $[Mn(CO)_6]^{+}$
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Solution:
- (c) $[Fe(CO)_4]^{2-}$
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.
$M-C \pi$ bond in metal carbonyl which is formed by the donatio of an electron pair from a filled $d$ orbital of metal into the vacant anti bonding $\pi$ orbtial of CO, strengthen the M-C $\sigma$ bond. This is called synergic effect.
