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Coordination Compounds - Importance and Applications of Coordination Compounds

Grade 12CBSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Analytical Chemistry: Coordination compounds are used in qualitative and quantitative analysis. For example, the detection of Ni2+Ni^{2+} is done using dimethylglyoxime (DMG) which forms a rosy-red complex [Ni(DMG)2][Ni(DMG)_2]. EDTA is used in complexometric titrations to estimate the hardness of water (Ca2+Ca^{2+} and Mg2+Mg^{2+} ions).

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Metallurgy: Extraction of metals like Gold (AuAu) and Silver (AgAg) involves the formation of cyanide complexes. For example, gold is extracted as [Au(CN)2]−[Au(CN)_2]^-. Purification of Nickel is achieved through the Mond's Process by forming the volatile complex [Ni(CO)4][Ni(CO)_4].

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Biological Importance: Several vital biological molecules are coordination compounds. Chlorophyll is a coordination compound of Magnesium (Mg2+Mg^{2+}), Hemoglobin (the oxygen carrier in blood) is a coordination compound of Iron (Fe2+Fe^{2+}), and Vitamin B12B_{12} (Cyanocobalamine) is a coordination compound of Cobalt (Co3+Co^{3+}).

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Industrial Catalysts: Coordination compounds are used as catalysts in industrial processes. Wilkinson's catalyst, [RhCl(PPh3)3][RhCl(PPh_3)_3], is used for the hydrogenation of alkenes.

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Medicinal Chemistry: Chelation therapy is used to remove toxic metals from the body. For example, excess Copper (CuCu) and Iron (FeFe) are removed by chelating ligands like D-penicillamine and desferrioxamine B. EDTA is used to treat Lead (PbPb) poisoning.

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Cancer Treatment: The coordination compound cis-platin, cis−[PtCl2(NH3)2]cis-[PtCl_2(NH_3)_2], is effectively used as an anti-tumor agent in the treatment of cancer.

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Electroplating: Stable coordination complexes like [Ag(CN)2]−[Ag(CN)_2]^- and [Au(CN)2]−[Au(CN)_2]^- are used in baths for smooth and even electroplating of silver and gold respectively.

📐Formulae

Ni+4CO→330−350K[Ni(CO)4]→450−470KNi+4CONi + 4CO \xrightarrow{330 - 350 K} [Ni(CO)_4] \xrightarrow{450 - 470 K} Ni + 4CO

4Au(s)+8CN−(aq)+2H2O(aq)+O2(g)→4[Au(CN)2]−(aq)+4OH−(aq)4Au(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \rightarrow 4[Au(CN)_2]^-(aq) + 4OH^-(aq)

2[Au(CN)2]−(aq)+Zn(s)→[Zn(CN)4]2−(aq)+2Au(s)2[Au(CN)_2]^-(aq) + Zn(s) \rightarrow [Zn(CN)_4]^{2-}(aq) + 2Au(s)

[RhCl(PPh3)3] (Wilkinson’s Catalyst)[RhCl(PPh_3)_3] \text{ (Wilkinson's Catalyst)}

cis−[PtCl2(NH3)2] (Cis-platin)cis-[PtCl_2(NH_3)_2] \text{ (Cis-platin)}

💡Examples

Problem 1:

Explain how the hardness of water is estimated using coordination chemistry.

Solution:

Hardness of water is due to the presence of Ca2+Ca^{2+} and Mg2+Mg^{2+} ions. These ions form stable complexes with EDTA4−EDTA^{4-} (Ethylenediaminetetraacetate).

Explanation:

During titration, EDTA4−EDTA^{4-} reacts with Ca2+Ca^{2+} and Mg2+Mg^{2+} to form chelate complexes. The total hardness is determined by titrating a known volume of water against a standard solution of EDTAEDTA using Eriochrome Black T (EBT) as an indicator at pH≈10pH \approx 10.

Problem 2:

What is the role of coordination compounds in the purification of Nickel?

Solution:

Impure Nickel is reacted with Carbon Monoxide (COCO) to form a volatile complex, Nickel Tetracarbonyl, which is then decomposed to give pure Nickel.

Explanation:

This is known as Mond's Process. The reaction is: Ni+4CO→[Ni(CO)4]Ni + 4CO \rightarrow [Ni(CO)_4]. The impurities do not form volatile carbonyls and are left behind. The complex is then heated to a higher temperature (450−470K450-470 K) to recover pure metal: [Ni(CO)4]→Ni+4CO[Ni(CO)_4] \rightarrow Ni + 4CO.

Problem 3:

Name the coordination compound used as an oxygen carrier in the human body and specify the central metal ion.

Solution:

The coordination compound is Hemoglobin, and the central metal ion is Fe2+Fe^{2+} (Iron in +2 oxidation state).

Explanation:

Hemoglobin is a complex of Fe2+Fe^{2+} with a porphyrin ligand (heme) and a protein (globin). It binds reversibly with O2O_2 to transport it from the lungs to the tissues.