The metal carbonyls (and similar organometallic compounds) involve a combination of sigma bond, a pi bond and backbonding. The bond strengths under consideration are the metal-carbon bond and the carbon oxygen bond. Here is the original question:-
Predict the order of C−O bond strength in the following:-
I) [Mn(CO)X6]+
II) [Cr(CO)X6]
III) [V(CO)X6]−
All of these are isoelectronic, and hence whatever the difference of bond strengths, must arise from the difference in the resultant nuclear force of attraction. Since MnX+ has the highest charge density, I would assume that the M−C bond strength of the manganese compound is the strongest (vanadium being the weakest) and therefore, the C−O bond strength must follow the opposite order, as the strengthening of the metal carbonyl bond should weaken the carbon oxygen bond.
But the answer given is III
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