Importance of coordination compounds

Coordination compounds, such as the FeCl4- ion and CrCl3 6 NH3, are called such because they contain ions or molecules linked, or coordinated, to a transition metal.

They are also known as complex ions or coordination complexes because they are Lewis acid-base complexes.

The ions or molecules that bind to transition-metal ions to form these complexes are calledligands (from Latin, "to tie or bind").

The number of ligands bound to the transition metal ion is called the coordination number.

Coordination compound any of a class of substances with chemical structures in which a central metalatom is surrounded by nonmetal atoms or groups of atoms, called ligands, joined to it by chemical bonds.

Coordination compounds include such substances as vitamin B12, hemoglobin, and chlorophyll, dyes and pigments, and catalysts used in preparing organic substances.

Application :

Coordination compounds are used as catalysts for many industrial processes and have many applications in qualitative/quantitative chemical analysis within analytical chemistry.

The of coordination compounds has importance in biological system, the coordination compounds play a vital role in metallurgy and medicine.

For example it isused to detect cupric ions in the salt, when copper sulphate solution is mixed with aqueous ammonia, a deep blue complex soluble in water is formed.

There is a application of complexes in metallurgy as follows:

(a) Noble metals like silver and gold are extracted from their ore by the formation of cyanide complexes - dicyanoargentite and dicyanoaurate

(b) Metals can be purified by the formation and subsequent decomposition of their coordination compounds.

Nickel can be purified by its reaction with carbon monoxide to form the volatile complex, tetracarbonyl Nickel (0), which is decomposed thermally to yield pure Nickel.

The application of complexes in biological systems as follows:

(a) The haemoglobin red pigment of blood that acts as oxygen carrier is a coordination compound of iron.

(b) There is so many enzymes that regulate biological processes are metal complexes.

Carboxypeptidase is a protease enzyme that hydrolytic enzyme important in digestion, contains a zinc ion coordinated to several amino acid residues of the protein.

The applications of coordination compounds as catalysts in industrial processes as follows:

(a) In the polymerisation of ethene, The Ziegler-Natta catalyst is used which is a combination of titanium tetrachloride and tri ethyl aluminium.

(b) In the hydrogenation of alkenes, a complex metal catalyst is used

The applications of coordination compounds in analytical chemistry as follows:

(a) In the qualitative methods of analysis, complex formation is of immense importance in the identification and separation of most inorganic ions.

(When copper sulphate solution is mixed with aqueous ammonia, a deep blue complex soluble in water is formed. This reaction is used to detect cupric ions in the salt).

(b) The water hardness is estimated by titration with the sodium salt of EDTA, the calcium and magnesium ions in hard water forms the stable complexes, magnesium EDTA and calcium EDTA.

These ions can be selectively estimated due to the difference in the stability constants of magnesium and calcium EDTA complexes.