In coordination complexes, diastereomers are stereoisomers that are not mirror images of each other. Unlike enantiomers, they cannot be related as left and right hands, but they still have the same formula and connectivity of ligands around the central metal ion.
Here’s a explanation:
- Definition:
- Stereoisomers that are not mirror images are called diastereomers.
- They often differ in spatial arrangement of ligands around the metal center.
- Examples in Coordination Complexes:
- Octahedral complexes with formula [MA₂B₂C₂]:
- Can have facial (fac) and meridional (mer) forms.
- Fac: Three identical ligands occupy one face of the octahedron.
- Mer: Three identical ligands lie in a plane through the metal.
- Fac and mer are diastereomers because they are not mirror images.
- Square planar complexes can also show cis-trans isomerism, where cis and trans forms are diastereomers.
- Octahedral complexes with formula [MA₂B₂C₂]:
- Properties of Diastereomers:
- They have different physical properties: melting point, solubility, and sometimes color.
- They can be separated more easily than enantiomers because they are not identical in most properties.
In short: Diastereomers are non-mirror-image stereoisomers in coordination complexes, often arising from different spatial arrangements of ligands, such as fac-mer or cis-trans forms.