What is the Difference Between Square Planar and Tetrahedral Complexes?

The main difference between square planar and tetrahedral complexes lies in their coordination geometry and the number of electron pairs in the central atom. Here are the key differences:

1. Coordination Geometry: In square planar geometry, a central atom is surrounded by four constituent atoms, which form the corners of a square on the same plane. In tetrahedral geometry, a central atom is located at the center of four substituent atoms, which form the corners of a tetrahedron.
2. Number of Electron Pairs: Square planar complexes have 2 lone pairs of electrons on the central atom (AX4E2), while tetrahedral complexes have no lone pairs on the central atom (AX4).
3. Bond Angles: The bond angles in a square planar structure are 90 degrees, whereas the bond angles in a tetrahedral structure are 109.5 degrees.
4. Crystal Field Diagram: Square planar complexes have a four-tiered crystal field diagram, while tetrahedral complexes have a two-tiered crystal field diagram.

Both square planar and tetrahedral complexes have a coordination number of 4, meaning they have 4 ligands bound to the central atom. The different coordination geometries and electron pair arrangements lead to distinct molecular shapes, bond angles, and crystal field diagrams for each type of complex.

Comparative Table: Square Planar vs Tetrahedral Complexes

The main differences between square planar and tetrahedral complexes can be summarized in the following table:

Square planar complexes have a four-tiered crystal field diagram, while tetrahedral complexes have a two-tiered crystal field diagram. The square planar geometry is prevalent for transition metal complexes with a d^8 configuration, such as Rh(I), Ir(I), Pd(II), Pt(II), and Au(III). On the other hand, tetrahedral geometry is common for complexes where the metal has d^0 or d^10 electron configuration, with bond angles of 109.5° between the ligands.