Question

Give VBT description of the bonding in a square planar complex [Cu(NH₃) ₄]²⁺. Show orbital diagrams for free metal ion and metal ion in the complex. Which hybrid orbitals are used by metal for bonding? State magnetic nature of the complex.

Answer 1

[Cu(NH₃)₄]²⁺ (Square planar)

1. Oxidation state of copper is +2, Cu²⁺ Electron configuration of metal ion is [Ar]3d⁹.
2. Orbital diagram of free metal ion:
   
3. Because the complex is square planar Cu²⁺ must be dsp² hybridized. In order to make one d orbital vacant, unpaired electron of d orbital is transferred to the last 4p orbital. Thus,
   
4. One 3d orbital, one 4s orbital and two 4p orbitals of Cu²⁺ ion hybridize to produce four dsp² vacant hybrid orbitals. These orbitals overlap with filled orbitals of 4 ligand donor atoms.
   
5. The complex contains one unpaired electron. Therefore, it is paramagnetic.