Isomerism in complex ions

Molecules with the same molecular formula but a different orientation of bonds/arrangement of atoms in space.

Optical isomerism and cis-trans isomerism.

Two non-superimposable mirror images can be created when an octahedral complex has three bidentate ligands attached to the central ion (example on textbook pg. 382).

Square planar complexes with two pairs of ligands (e.g., cisplatin) can show cis-trans isomerism.

When two paired ligands are directly opposite each other it’s the trans isomer (diagonal) and when two paired ligands are next to each other it’s the cis isomer (horizontal).

• Cisplatin is the cis isomer as both pairs of ligands are next to each other.

• It’s counterpart is transplatin, which has different biological properties.

It stops cancer cells from reproducing.

It can stop normal cells from reproducing, causing hair loss and increasing susceptibility to infection as blood cells cannot reproduce. It may also cause kidney damage.

Octahedral complexes with four ligands of one type and two ligands of another type can exhibit cis-trans isomerism.

• If the two odd ligands are opposite one another (at 12 and 6) then it’s a trans isomer.

• If the two odd ligands are next to each other (at 2 and 4) then it’s a cis isomer.