In which compound synergic effect is present ?

Options

A. `[Ni(CO)_4]`
B. `[NiCl_4]^(2-)`
C. `[CuCl_4]^(2-)`
D. `[Mn(H_2O)_6]^(2+)`

Answer

A

Explanation

(a) Synergic bonding in transition metal carbonyl complexes. CO (carbonyl ligand) can interact with a transition metal in two ways : (i) It possesses a full sp - orbital on carbon, which can donate electron density to a transition metal and thereby form a bond. (ii) CO also possesses an empty p -orbital on carbon at 90 degrees to the sp- orbital. This empty p- orbital can accept electron density from a transition metal, again forming a bonding interaction. In organo-metallics, the effect is observed when a pi - back donation of `e^-` density occurs from an atomic orbital of one atom to the antibonding −pi orbital of another. The antibonding pi -orbital must be pi - acceptor ligand.