The key difference between square planar and tetrahedral complexes is that square planar complexes have a four-tiered crystal field diagram, but the tetrahedral complexes have a two-tiered crystal field diagram.
Crystal field theory is a theory in chemistry which describes the breaking of electron orbitals (mainly d and f orbitals) due to the static electric field produced by the anionic charge in the surrounding of an atom. The theory is very important in describing the properties of transition metal complexes. We can describe the structures of square planar and tetrahedral complexes as well.
CONTENTS
1. Overview and Key Difference
2. What are Square Planar Complexes
3. What are Tetrahedral Complexes
4. Side by Side Comparison – Square Planar vs. Tetrahedral Complexes in Tabular Form
5. Summary
What are Square Planar Complexes
Square planar complexes are coordination complexes that have a central metal atom surrounded by four constituent atoms in corners of the same square plane. The bond angles of the bonds in this structure are 90°. Transition metals having the electron configuration ending d8 form coordination complexes having this molecular geometry. For example, Rh(I), Ir(I), Pd(II), etc. The coordination number for a square planar complex is four.
We can describe the structure of these complexes using the Crystal field theory (CFT). According to this theory, a square planar complex has a four-tiered crystal field diagram. And, this four-tiered splitting is named D4h. The resulting four energy levels are named dx2-y2, dxy, dz2, and [dxz, dyz]. Moreover, there is a specific relationship between square planar geometry and tetrahedral geometry. We can convert a tetrahedral geometry into a square planar geometry by flattening the tetrahedron. And, this conversion provides a pathway for the isomerization of the tetrahedral complexes.
What are Tetrahedral Complexes?
Tetrahedral complexes are coordination complexes that have a central metal atom surrounded by four constituent atoms in corners of a tetrahedron. The bond angles of the bonds in this structure are about 109.5°. However, if the constituents are different from each other, the bond angles vary. There are two types of transition metals that can form this type of complex: metals having d0 configuration and d10 configuration.
Moreover, according to the crystal field theory, the tetrahedral complexes have a two-tiered crystal field diagram. The two energy levels of this diagram include two sets of orbitals: dxy, dxz, dyz in one energy level, and dx2-y2, dz2 in the other set.
What is the Difference Between Square Planar and Tetrahedral Complexes?
Crystal field theory is very important in describing the properties of transition metal complexes, as well as the structures of square planar and tetrahedral complexes. The key difference between square planar and tetrahedral complexes is that the square planar complexes have a four-tiered crystal field diagram, but the tetrahedral complexes have a two-tiered crystal field diagram.
Moreover, transition metals having their electron configurations ending with d8 configuration tend to form square planar complexes, while metals having d0 configuration and d10 configuration tend to form tetrahedral complexes.
The below infographic shows more comparisons regarding the difference between square planar and tetrahedral complexes.
Summary – Square Planar vs. Tetrahedral Complexes
Crystal field theory is very important in describing the properties of transition metal complexes. We can describe the structures of square planar and tetrahedral complexes as well. The key difference between square planar and tetrahedral complexes is that the square planar complexes have a four-tiered crystal field diagram, whereas tetrahedral complexes have a two-tiered crystal field diagram.
Reference:
1. Mott, Vallerie. “Introduction to Chemistry.” Lumen, Available here.
2. “Bonding in Coordination Compounds: Crystal Field Theory.” Boundless Chemistry, Lumen, Available here.
3. “Crystal Field Theory.” LibreTexts, Available here.
Image Courtesy:
1. “Square-planar-3D-balls” (Public Domain) via Commons Wikimedia
2. “Tetrahedral-3D-balls” (Public Domain) via Commons Wikimedia