Question

Which cordination compound has longest carbon oxygen bond length?

Answer 1

ANS: [Mn(CO) 6] ^+

Because it has least electron density . Hence it readily accepts sigma electron density but is reluctant in backdonation. Hence weaker M-C bond and stronger C=O bond

Answer 2

Carbon monoxide bonds to back-bonding." The bonding has three components, giving rise to a partial triple bond. A sigma bond arises from overlap of the nonbonding (or weakly anti-bonding) sp-hybridized electron pair on carbon with a blend of d-, s-, and p-orbitals on the metal. A pair of π bonds arises from overlap of filled d-orbitals on the metal with a pair of π-antibonding orbitals projecting from the carbon atom of the COCO. The latter kind of binding requires that the metal have d-electrons, and that the metal is in a relatively low oxidation state (<+2<+2) which makes the back donation

As electrons from the metal fill the π-antibonding orbital of COCO, they weaken the carbon-oxygen bond compared with free carbon monoxide, while the metal-carbon bond is strengthened. Because of the multiple bond character of the M−COM−CO linkage, the distance between the metal and carbon atom is relatively short, often <1.8 Å<1.8 Å, about 0.2 Å0.2 Åshorter than a metal-alkyl bond.

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