Stereoisomerism in Transition Element Complexes (Cambridge (CIE) A Level Chemistry): Flashcards

Cis-trans isomerism in complexes is a type of stereoisomerism found in square planar and octahedral complexes with two pairs of different ligands. In the cis isomer, identical ligands are adjacent; in the trans isomer, they are opposite each other.

Cisplatin is polar because the two electronegative Cl ligands are on the same side, creating a charge imbalance that allows it to bind to DNA. Transplatin is non-polar because the ligands are opposite each other, so the charges cancel.

True. Such complexes have no plane of symmetry and exist as non-superimposable mirror images — the defining feature of optical isomers.

In a trans isomer of an octahedral complex, the two different ligands are positioned opposite each other, making the complex non-polar.

An octahedral complex displays cis-trans isomerism when it has two ligands that are different from the other four. These two different ligands can be either adjacent (cis) or opposite (trans).

False. The two optical isomers rotate the plane of polarised light in opposite directions. This is their only difference in properties.

Optical isomers are non-superimposable mirror images of each other. They have no plane of symmetry and differ only in the direction in which they rotate the plane of polarised light.

In the cis isomer, the two H₂O ligands are on the same side. The oxygen atoms in water are more electronegative than the nitrogen atoms in NH₃, creating a partial negative charge on one side and making the complex polar.

Cisplatin is a square planar complex with two Cl^- and two NH₃ ligands.