Coordination compounds are chemical compounds in which a central metal atom or ion is surrounded by ions or molecules called ligands. These compounds exhibit unique properties such as coloured appearance, magnetic behavior, and ability to form stable complexes. Because of these special characteristics, coordination compounds play an important role in various fields.
1. Applications in Analytical Chemistry
Coordination compounds are extensively used in analytical chemistry for the detection, separation, and estimation of metal ions.
- Certain ligands form stable and colored complexes with metal ions, making their identification easier.
- EDTA is an important coordination compound used in complex metric titrations to determine the hardness of water.
- It forms stable complexes with calcium and magnesium ions present in hard water.
2. Applications in Metallurgy
Coordination compounds play an important role in the extraction and purification of metals. In the cyanide process, gold and silver are extracted from their ores by forming soluble cyanide complexes.
4Au + 8CN − + O2 + 2H2O → 4[Au(CN)2] − + 4OH −
3. Biological Importance
Many coordination compounds are naturally present in living organisms and are essential for biological activities. Hemoglobin, an iron coordination compound present in blood, transports oxygen throughout the body.
- Chlorophyll, containing magnesium, is responsible for photosynthesis in plants.
- Vitamin B₁₂ contains cobalt and is essential for the formation of red blood cells.
- Several enzymes also contain coordinated metal ions which help in biochemical reactions.
4. Medicinal Applications
Certain coordination compounds are used in medicine for treatment of diseases.
- Cisplatin, a platinum coordination compound, is widely used in chemotherapy for the treatment of cancer.
- EDTA is used in the treatment of lead poisoning because it forms stable complexes with toxic metal ions and helps remove them from the body.
- Radioactive coordination compounds are also used in diagnosis and treatment of certain diseases.
5. Applications in Industry
Coordination compounds are widely used as catalysts in industrial processes.
- Wilkinson catalyst is used in hydrogenation reactions.
- Zeigler–Natta catalysts are used in the manufacture of polymers such as polythene.
- Coordination compounds are also used in electroplating, textile dyeing, tanning, and manufacture of paints and pigments.
6. Applications in Photography
Coordination compounds are used in photography for fixing photographic films. Sodium thiosulphate dissolves unreacted silver bromide by forming a soluble complex.
AgBr + 2S2O32− → [Ag(S2O3)2 ]3− + Br −