Stereoisomers are compounds that have the same atom-to-atom bonding sequence but a different arrangement of the atoms in space.
Square-planar and octahedral complexes may have different stereoisomers
This is because in these geometries, the opposite positions are different to the adjacent positions.
See the diagrams below for complexes having two different types of ligands.
The stereoisomer of each pair where two ligands on adjacent positions are the same is the cis isomer.
The stereoisomer of each pair where the two ligands on opposite positions are the same is the trans isomer.
The cis and trans isomers of coordination complexes have different physical properties.
Square-planar and octahedral complexes may have different stereoisomers
This is because in these geometries, the opposite positions are different to the adjacent positions.
See the diagrams below for complexes having two different types of ligands.
 trans |  cis |  cis |  trans |
The stereoisomer of each pair where two ligands on adjacent positions are the same is the cis isomer.
The stereoisomer of each pair where the two ligands on opposite positions are the same is the trans isomer.
The cis and trans isomers of coordination complexes have different physical properties.
For example cis and trans isomers may have different melting points or different colours.