Question

Q)What would be the board level definition of synergic effect ?????
And how synergic effect strengthens the bond between metal and the carbonyl group ??????
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Answer 1

It is an effect arising between two or more elements or substances, when they are combined together they produces a greater effect than the sum of the individual effect.

CO (Carbonly ligand) can interact with transition metal in two ways

1. It possesses a full sp-orbital on carbon, which can donate electron density to the transition metal and thereby forming a Bond. ( Eg. water, amines.)
2. CO also possesses and empty p-orbital on carbon at 90 deg at the sp-orbital. This empty p-orbital can accept electron density for a transition metal, again forming a bonding interaction.

These two effects happens at the same time, enhancing the strength of each interaction. As the CO ligand donates more electron density to the metal (from sp-orbital) the metal becomes more electron rich and able to donate more electron density to the empty p-orbital on the carbon. In short, the strength of each bonding interaction is in part dependent on the other.