Square Planar Complexes (Edexcel International A Level (IAL) Chemistry): Revision Note

Exam code: YCH11

Stewart Hird

Last updated

Square Planar Complexes

  • 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

Chemistry of Transition Elements - Square Planar Complexes, downloadable AS & A Level Chemistry revision notes

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

  • Cis-platin has beneficial medical effects by binding to DNA in cancer cells, trans-platin cannot be used in cancer treatment

Chemistry of Transition Elements - Cis-trans in Square Planar, downloadable AS & A Level Chemistry revision notes

Cis-platin is an example of a square planar transition element complex that exhibits geometrical isomerism

  • 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

Chemistry of Transition Elements - Cis-Platin Mode of Action Current SP, downloadable AS & A Level Chemistry revision notes

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

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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Content Creator

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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