Edexcel A Level Chemistry:复习笔记6.2.7 Cis-platin



  • Sometimes, complexes with four coordinate bonds may adopt a square planar geometry instead of a tetrahedral one
    • Cyanide ions (CN-) are the most common ligands to adopt this geometry
    • An example of a square planar complex is cisplatin
  • The bond angles in a square planar complex are 90o


Cisplatin is an example of a square planar complex

  • In the 1960s the drug cis-platin was discovered, which has been extremely effective in treating a number of different types cancer such as testicular, ovarian, cervical, breast, lung and brain cancer
  • Cancer cells grow and replicate much faster than normal cells
  • Cis-platin is a square planar molecule that has a geometric isomer with the side groups in different positions


The structures of cis-platin and trans-platin

  • The cis-platin works by binding to the nitrogen atoms on the bases in DNA
  • The cis-platin passes through the cell membrane and undergoes ligand exchange where the chlorines are replaced by water molecules
  • The nitrogen is a better ligand than water and forms dative covalent bonds with the cis-platin
  • The cis-platin distorts the shape of the DNA and prevents the DNA from replicating


The process by which cis-platin binds to DNA and prevents replication

Adverse Effects

  • Cis-platin binds to healthy cells as well as cancerous cells, but affects cancer cells more as they are replicating faster
  • Unfortunately, this means that other healthy cells which replicate quickly, such as hair follicles, are also affected by cis-platin
  • This is why hair loss is a side-effect of people undergoing cancer treatment
  • Despite this drawback, cisplatin is a highly effective drug and society needs to find a balance between the adverse effects of drugs and their therapeutic value
  • New therapeutic pathways are constantly under development that aim to deliver drugs that target cancer cells while leaving healthy cells untouched