Preparation and Application of coordination compounds.
(1) Preparation : Coordination compounds are generally prepared by the application of the following methods,
(i) Ligand substitution reaction : A reaction involving the replacement of the ligands attached to the central metal ion in the complex by other ligands is called a ligand substitution reaction.
[Cu(H2O)4]2+(aq) + 3NH3(aq) → [Cu(NH3)4]2+ (aq) + 4H2O(l)
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(ii) Direct mixing of reagent :
PtCl2 + 2H2N – CH2 – CH2 – NH2 → [Pt(en)2 Cl2]
(en) (Dichloro bis ethylene diammine platinum
(iii) Redox reactions : In these reactions, either oxidation or reduction is involved
2CO(NO3)2 + 8NH3 + 2NH4NO3 + H2O2
2[CO(NH3)NO2](NO3)2 + 2H2O
Penta ammine nitrocobalt (II) nitrate.
Application
(1) Estimation of hardness in water, as Ca++ and Mg2+ ions form complexes with EDTA.
(2) Animal and plant world e.g. chlorophyll is a complex of Mg2+ and haemoglobin is a complex of Fe2+ vitamin B12 is a complex of Co2+.
(3) Electroplating of metals involves the use of complex salt as electrolytes e.g. K[Ag(CN)2] in silver plating.
(4) Extraction of metals e.g. Ag and Au are extracted from ores by dissolving in NaCN to form complexes.
(5) Estimation and detection of metal ions e.g. Ni2+ ion is estimated using dimethyl glyoxime.
(6) Medicines e.g. cis-platin i.e. cis [PtCl2 (NH3)2] is used in treatment of cancer.
