Transplatin

trans-Dichlorodiammineplatinum is the trans isomer of the coordination complex with the formula trans-PtCl₂₂, sometimes called transplatin. It is a yellow solid with low solubility in water but good solubility in DMF. The existence of two isomers of PtCl₂₂ led Alfred Werner to propose square planar molecular geometry. It belongs to the molecular symmetry point group D_2h.

Preparation and reactions

The complex is prepared by treating Cl₂ with hydrochloric acid.
Many of the reactions of this complex can be explained by the trans effect. It slowly hydrolyzes in aqueous solution to give the mixed aquo complex trans-Cl. Similarly it reacts with thiourea to give colorless trans-Cl₂. In contrast, the cis isomer gives Cl₂. Oxidative addition of chlorine gives trans-PtCl₄₂.

Medicinal chemistry

trans-Dichlorodiammineplatinum has had far less impact on medicinal chemistry compared to its cis isomer, cisplatin, which is a major anticancer drug. Nonetheless, replacement of the ammonia with other ligands has led to highly active drugs that have attracted much attention.