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Applications of Coordination Compounds

Last Updated : 29 Nov, 2022
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Chemical compounds made up of an array of anions or neutral molecules linked to a central atom by coordinate covalent bonds are known as coordination compounds. Coordination compounds are also known as coordination complexes. Ligands are the molecules or ions that are bonded to the central atom (also known as complexing agents).

Coordination Compounds

Coordination compounds are a type of compound that belongs to the complex compound class. This is due to the chemistry involved with these molecules. Transition metals have the unique ability to generate coordination complexes. This is because of the high charge-to-mass ratio and the availability of d-orbitals.

Coordination chemistry developments have produced a variety of complex chemicals that we employ in a variety of sectors. Coordination chemicals are widely used in a variety of sectors. These include naming a few, mining and metallurgy, medical sciences, and so on.

Examples of coordination compounds

Coordination complexes are found in many biological substances. There are a plethora of additional coordination molecules that play critical roles in biological processes. During these physiological activities, the bodies make and consume a large number of complex chemicals. Chlorophyll is required for photosynthesis in plants. This chlorophyll is a combination of magnesium and porphyrin. Many of the enzymes that catalyze biological processes in our bodies are coordination complexes. Carboxypeptidase is one such example. It is a coordination molecule that also functions as an enzyme. It is required to catalyze the digestive process.

Properties of Coordination Compounds

  1. The existence of unpaired electrons that absorb light in their electronic transitions colors the coordination compounds created by the transition elements. Complexes containing Iron(II) might be green or pale green in color, whereas coordination compounds containing Iron(III) are brown or yellowish-brown in color.
  2. Because of the presence of unpaired electrons, the related coordination complexes have a magnetic character when the coordination center is a metal.
  3. Coordination compounds have a wide range of chemical reactivity. They can be involved in both inner-sphere and outer-sphere electron transfer reactions.
  4. Complex compounds containing certain ligands have the ability to catalyze or stoichiometrically help in the transition of molecules.

Werner’s Theory of Coordination Compounds

Werner developed a theory in 1893 to explain the structures, production, and nature of bonding in coordination molecules. Werner’s theory of coordination compounds is the name given to this hypothesis. Werner received the Nobel Prize in Chemistry in 1913 as the first inorganic chemist. He investigated a wide range of complicated chemicals derived from the interaction of cobalt chloride and ammonia. The core metals of coordination compounds have two valencies.

  1. Primary Valency: Primary valencies are those that a metal exhibits when simple salts are formed like NaCl, CuSO4, and so on. In current parlance, it denotes the metal’s oxidation number. For example, the major valencies of Co in CoCl3 are 3 and the oxidation state is +3. Ionizability exists for the primary valencies. These are written beyond the scope of cooperation. These are non-directional and do not offer complicated compounds in any shape. [Co(NH3)6]Cl3, 3 main valencies, +3 oxidation state.
  2. Secondary valency: Metals’ secondary valency is determined by either negative ions or neutral molecules, or both. In current parlance, it denotes the metal’s coordination number. Within the coordinating sphere, secondary valencies are written. These are directed in character and give the complex a definite geometry. These cannot be ionized. [Co(NH3)6] is an example. Cl3 has a coordination number of 6.

Importance of Coordination Compounds

Coordination compounds, such as the FeCl4 ion are so named because they contain ions or molecules that are linked to, or coordinated with, a transition metal, because they are Lewis acid-base complexes, they are also known as complex ions or coordination complexes. Ligands are the ions or molecules that bind to transition-metal ions to generate these complexes. The coordination number is the number of ligands attached to the transition metal ion. A coordination complex is any of a class of chemicals with chemical structures in which a central metal atom is surrounded by nonmetal atoms or groups of atoms, known as ligands, that are chemically linked to it. Coordination compounds include vitamin B12, hemoglobin, and chlorophyll, as well as dyes and pigments, and catalysts utilized in the synthesis of organic molecules.

Applications of Coordination Compounds

  1. Colors are assigned to coordination compounds. As a result, they have a widespread place in businesses that require vivid colorations. Phthalocyanine is a type of coordination complex that is widely used in the dyes and pigments industry. They use it to dye fabrics a specific color.
  2. Some cyanide compounds are used to electroplate a protective layer on surfaces. There are complexes that make use of coordination chemicals in photography.
  3. EDTA is another complicated chemical that we utilize to determine the hardness of the water. Coordination compounds can also be used as catalysts, which is one of their many applications. They are also gaining popularity in the polymer industry these days.
  4. The concept of coordination compounds is used far too frequently these days in the extraction of metals from their ores. The extraction of nickel and cobalt entails the utilization of these chemicals in a significant way. These metals are recovered via hydrometallurgical techniques that need a large number of complicated ions.
  5. As more coordination chemicals are synthesized, scientists and engineers now have a plethora of possibilities for refining and optimizing the processes that necessitate them.
  6. Hemoglobin is made up of Heme complex-ions with tetrapyrrole Porphyrin ring structures and a core Fe2+ ion. Vitamin B12 is made up of a tetrapyrrole porphyrin ring complex with a core Co+3 ion and has a coordination number of 6.
  7. Cisplatin is a chemotherapy drug that is used to treat cancer.
  8. The Ziegler-Natta catalyst, a mixture of titanium tetrachloride and triethyl aluminum, is employed in the polymerization of ethene.
  9. A complex metal catalyst is used in the hydrogenation of alkenes.
  10. Complex formation is critical in the identification and separation of most inorganic ions using qualitative methods of investigation. When copper sulfate solution is combined with aqueous ammonia, a deep blue complex that is water-soluble is generated. This reaction is used to identify the presence of cupric ions in salt.

Sample Problems

Question 1: Why do we use coordination compounds to separate metals in extractive metallurgy?


These compounds are commonly used in the separation of metals during the extractive metallurgy process. This is due to the fact that these complex ions have the unique property of selective precipitation and solubility.

Question 2: What is meant by the chelate effect?


A five or six membered ring is created when a bidentate or polydentate ligand has donor atoms that are positioned in such a way that when they coordinate with the central metal ion. This is known as the Chelate effect. As a result, the complex’s stability improves.

Question 3: Why are tetrahedral complexes high spin?


Because of the narrow splitting energy gap, electrons are not compelled to pair, resulting in a significant number of unpaired electrons, i.e. high spin.

Question 4: Explain why nickel does not form low spin octahedral complexes.


Even with a high field ligand, electron pairing does not occur in octahedral complexes, hence Ni does not form low spin octahedral complexes.

Question 5: What is geometric isomerism?


Geometric isomerism refers to the isomerism that occurs in heteroleptic complexes as a result of different conceivable geometric configurations of the ligands.

Question 6: What is a coordination entity?


The coordination entity is formed when the core metal atom is surrounded by ligands or ions and forms a complex.

Question 7: What is linkage isomerism?


This isomerism occurs in coordination compounds containing ambidentate ligands. For example, in the thiocyanate ligand NCS, this ligand can be linked to the central metal atom via the sulphur or nitrogen side, resulting in two linkage isomers.

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