Application Of Coordination Compounds

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  • The structures of certain coordination compounds can also have isomers, which can change their interactions with other chemical agents. The binding between metal and ligands is studied in metals, tetrahedral, and octahedral structures. There are many pharmaceutical and biological applications of coordination complexes and their isomers.
  • Finally the application of coordination compounds in general, the concept of coordination compounds in the extraction of metals from their ores too frequently these days. Extraction of nickel and cobalt involves a major use of these compounds. These metals are extracted by hydro-metallurgical processes requiring a lot of complex ions.
  • Metal ions can complex with a variety of molecular species to form coordination compounds/ complex ions.
  • These coordination compounds/complex ions differ appreciably from each other and also from their constituent species.
  • These aspects of coordination compounds/complex ions have been exploited in many ways.
  • Some of the major applications of the coordination compounds are described below.

i) In analytical chemistry

  • Formation of coordination compounds/complex ions has important role in analytical chemistry. It is used for either separating or estimating only one particular ion in the presence of other ions.
  • This is done by converting all ions except the one into stable complex ions by adding a suitable reagent (acting as ligand) into the solution.
  • This reagent forms stable complexes with all the ions except the desired one.
  • This desired ion thus remains as free ion in the solution.
  • These complex ions would no longer give the chemical reactions of the constituent ions.
  • So, the solution will give test/reactions only of the ion left un-complexed in the solution.
  • The ion which exists in the free ionic form in the solution then can be estimated or separated by suitable chemical method.
  • This application is illustrated by taking a solution containing both Cu2+ and Cd2+ions.
  • To estimate or separate one of these ions, we generally proceed as follows:

Application of Coordination Compounds with. T ransition Metal Ions in the Chemical. Industry—A Review. Jacek Malinowski 1, Dominika Zych 1, Dagmara Jacewicz 1, Barbara Gawdzik 2,.

a) To the solution containing Cu2+ and Cd2+ ions, an excess of KCN solution is added.

b) KCN dissociates in the solution to give CN– ions which form cyano complexes with both the ions, i.e.,[Cu(CN)4]2- and [Cd(CN)4]2-.

c) On passing H2S through the solution, cadmium gets precipitated as cadmium sulphide (CdS) despite its larger solubility.

Explanation

When KCN is added to a solution containing Cu2+ and Cd2+, both the ions get complexed to form [Cu(CN)4]2- and [Cd(CN)4]2- complex ions in accordance with the reactions,

Cu2+ + 4CN– ⇌ [Cu (CN)4]2-

Cd2+ + 4CN- ⇌ [Cd (CN)4]2-

The complex [Cu (CN)4]2- is more stable than the complex [Cd(CN)4]2–. It means that the equilibrium concentration of free Cd2+ in the solution is much higher than that of free Cu2+. So, when H2S is passed through the solution only CdS gets precipitated.

  • Nickel can be separated/identified / estimated by forming its complex with dimethylglyoxime. Nickel dimethylglyoixme is pink in colour.

ii) For the estimation of hardness of water

  • Hardness of water is confirmed if there is the presence of Ca2+ and Mg2+ ions in water.
  • There is formation of stable complexes with Ca2+ and Mg2+ by EDTA. So, estimation of the total hardness of water can be done by simple volumetric titration of water with EDTA.
  • Since, the stability constants of Ca2+ EDTA and Mg2+ EDTA complexes is different, hence the selective estimation of the two ions can be done.

iii) For softening of water

  • Ca2+ and Mg2+ ions which cause hardness can form stable complexes with EDTA and polyphosphates.
  • So, Ca2+ and Mg2+ ions present in water get trapped by these reagents by complexation which makes the water soft.

iv) In electroplating

  • There are various reasons of utilizing formation of complex ions in electroplating:

a) Complexes are more stable than the simple ions in solution towards oxidation, reduction, hydrolysis, etc.

b) Complexes give a controlled supply of metal ions in the solution. It is because, the complexes are reasonably stable, and also they dissociate to very small extent. As a result, the concentration of free metal ions is maintained at low level in solution. This low concentration of metal ions in solution gives better deposit during electroplating.

The complexes commonly used in electroplating are:

K[Ag(CN)2] for silver plating and K[Au(CN)2] for gold plating.

v) In extractive metallurgy

  • The usefulness of complex formation is observed in the extraction of metals like the extraction of silver from Ag2S by complexing Ag+ with CN– in accordance with the reaction.

Ag2S + 4NaCN ⇌2Na[Ag(CN)2] + Na2S

  • The metallic silver is recovered by treating the solution of Na[Ag(CN)2] with zinc dust.

2Na[Ag(CN)2] + Zn → Na2[Zn(CN)4] + 2Ag

  • There are however many more interesting application of complex formation in the field of extractive metallurgy.

vi) In the field of medicine

Application of coordination compounds in agriculture
  • Complexes have been found useful in the treatment of certain diseases. For example: the platinum complex, cis-[PtCl2(NH3)2] known as cis-platin is found useful in cancer chemotherapy.

vii) In nature

  • Chelates are special type of complexes. Formation of chelates in living systems has hot much biological significance.
  • For example: chlorophyll is a complex of Mg2+ with porphyrin, hemoglobin is a complex of Fe2+with porphyrin. Vitamin B12 is a complex of Co2+.

viii) In modifying the redox behavior of metal ions

Application
  • Complexation leads to changes in the redox potential of the metal ions.
  • This aspect of complexation has been utilized in catalyzing certain biochemical reactions.

Practical Applications of Coordination Compounds

Topic: Coordination Compounds, Test No.: 03, Total MCQs: 10

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Coordination Compounds List

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The correct statement with respect to the complexes Ni(CO)4 and [Ni(CN)4]2– is
both have tetrahedral geometry
have tetrahedral and square planar geometry respectively
[Cr(H2O)4(O2N)]Cl2
[Cr(H2O)4Cl(ONO)Cl
The IUPAC name for the complex [Co(NO2)(NH3)5]Cl2 is
nitrito-N-pentaamminecobalt (II) chloride
pentaammine nitrito-N-cobalt (III) chloride
Potassium tetracyanatonickelate (II)
Potassium tetracyanonickel (III)
The IUPAC name of the complex [Co (NH3)4 Cl2] Cl is
tetraammine dichloro cobalt (III) chloride
tetraammine dichloro cobalt (IV) chloride
The IUPAC name of the coordination compound K3[Fe(CN)6] is
Potassium hexacyanoferrate (III)
tripotassium hexcyanoiron (II)
1.41 BM
5.46 BM
The number of unidentate ligands in the complex ion is called
Coordination number
oxidation number
The number of water molecule(s) directly bonded to the metal centre in CuSO4× 5H2O is

Application Of Coordination Compounds In Agriculture

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Application Of Coordination Compounds In Analytical Chemistry

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Application Of Coordination Compounds In Biological System

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