Ligands are broadly classified into two classes classical and non-classical ligands, depending on their donor annd acceptor ability. Classical ligands form classical complexes while non-classical ligands form non-classical complex. Bonding mechanism in non-classical is called synergic bonding.
Q. Synergic bonding is absent in:

Options

A. `[Mo(CO)_(6)]`
B. `[Cr(CO)_(3)(B_(3)N_(3)H_(6)]`
C. `[Sc(CO)_(6)]^(3+)`
D. `[Ni(CN)_(4)]^(4-)`

Answer

C

Explanation

`overset(+III)(Sc):3d^(@)4s^(@)`, as d-orbitals at `overset(+III)(Sc)` are empty, hence, there is no synergic bonding in `[Sc(CO)_(6)]^(3+)`.