Chemistry · Ch 5 — Coordination Chemistry
Cisplatin
Cisplatin
Cisplatin, cis-[Pt(NH₃)₂Cl₂], is a square planar platinum(II) coordination complex in which the two identical ligands of each pair (the two NH₃ and the two Cl) occupy positions adjacent to each other on the square plane, rather than across from each other -- the cis geometrical isomer discussed in Section 5.5.2. As a platinum-based anticancer drug, cisplatin undergoes hydrolysis inside the cell and then reacts with DNA to produce various crosslinks; these crosslinks physically hinder DNA replication and transcription, which in turn results in inhibition of cell growth and ultimately cell death. Cisplatin a …
Worked out. Only the CIS isomer of [Pt(NH₃)₂Cl₂] is clinically active as an anticancer drug; the corresponding trans isomer (transplatin) is essentially therapeutically inactive against the same tumours despite having the identical molecular formula. This is a striking real-world illustration of why the geometrical (cis/trans) isomerism covered in Section 5.5.2 is not just a structural curiosity -- for square planar [MA₂B₂] complexes, the spatial arrangement of otherwise-identical ligands can be the entire difference between a life-saving drug and an inactive compound, since only the cis arrangement can form t …