Discuss briefly giving an example in each case the role of coordination compounds in: (i) biological systems (iii) analytical chemistry (ii) medicinal chemistry and (iv) extraction/metallurgy of metals
(i) Biological systems Several naturally occurring biologically important compounds are coordination compounds. Thus, chlorophyll is a coordination compound containing Mg(II) ions. It is green pigment present in plants and is used in photosynthesis. (ii) Medicinal chemistry To remove metal poisoning, complexing agents are used, cis platin [PtCl2(NH3)2] is used in cancer chemotherapy. (iii) Analytical chemistry Complex formation is used in qualitative scheme of analysis. In group I analysis, silver ion is separated from the precipitate of AgCl,Hg2Cl2 and PbCl2. Aqueous ammonia is added to the ppt. AgCl dissolves due to formation of soluble complex. AgCl+2NH3⇌[Ag(NH3)2]Cl (iv) Extraction/metallurgy of metals Metals such as gold and silver are extracted by complex formation technique. Cyanide process is used for extraction of silver and gold from its ore. Ag2S+4NaCN→2Na[Ag(CN)2]+Na2S 2Na[Ag(CN)2]+Zn→Na2[Zn(CN)4]+2Ag
