Tetrahedral and Square Planar Complexes
Learning Objective
- Discuss the d-orbital degeneracy of square planar and tetrahedral metal complexes.
Key Points
- In tetrahedral molecular geometry, a central atom is located at the center of four substituents, which form the corners of a tetrahedron.
- Tetrahedral geometry is common for complexes where the metal has d0 or d10electron configuration.
- The CFT diagram for tetrahedral complexes has dx2−y2 and dz2orbitals equally low in energy because they are between the ligand axis and experience little repulsion.
- In square planar molecular geometry, a central atom is surrounded by constituent atoms, which form the corners of a square on the same plane.
- The square planar geometry is prevalent for transition metal complexes with d8 configuration.
- The CFT diagram for square planar complexes can be derived from octahedral complexes yet the dx2-y2 level is the most destabilized and is left unfilled.
Terms
- degeneracyHaving the same quantum energy level.
- ligandAn ion, molecule, or functional group that binds to another chemical entity to form a larger complex.
- substituentsAny atom, group, or radical substituted for another, or entering a molecule in place of some other part which is removed.
Tetrahedral Complexes
In tetrahedral molecular geometry, a central atom is located at the center of four substituent atoms, which form the corners of a tetrahedron. The bond angles are approximately 109.5° when all four substituents are the same. This geometry is widespread, particularly for complexes where the metal has d0 or d10 electron configuration.
Square Planar Complexes
In square planar molecular geometry, a central atom is surrounded by constituent atoms, which form the corners of a square on the same plane. The geometry is prevalent for transition metal complexes with d8 configuration. This includes Rh(I), Ir(I), Pd(II), Pt(II), and Au(III). Notable examples include the anticancer drugs cisplatin [PtCl2(NH3)2] and carboplatin.
The removal of a pair of ligands from the z-axis of an octahedron leaves four ligands in the x-y plane. Therefore, the crystal field splitting diagram for square planar geometry can be derived from the octahedral diagram. The removal of the two ligands stabilizes the dz2 level, leaving the dx2-y2 level as the most destabilized. Consequently, the dx2-y2 remains unoccupied in complexes of metals with the d8 configuration. These compounds typically have sixteen valence electrons (eight from ligands, eight from the metal).
Show Sources
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Terry Kennair, Transition Metals. September 17, 2013."
http://cnx.org/content/m15057/latest/
OpenStax CNXCC BY 3.0.
"Tetrahedral molecular geometry."
http://en.wikipedia.org/wiki/Tetrahedral_molecular_geometryWikipedia
CC BY-SA 3.0.
"Tetrakis(triphenylphosphine)palladium(0)-3D-sticks."
http://en.wikipedia.org/wiki/File:Tetrakis(triphenylphosphine)palladium(0)-3D-sticks.pngWikipedia
Public domain.
"Nickel-carbonyl-2D."
http://en.wikipedia.org/wiki/File:Nickel-carbonyl-2D.pngWikipedia
Public domain.
"Boundless."
http://s3.amazonaws.com/figures.boundless.com/50955533e4b007ceedc6e399/carboplatin.jpgAmazon Web Services
Public domain.
Licenses and Attributions
More Study Resources for You
Show More