What is the Difference Between Coordination Complex and Double Salt

The main difference between coordination complex and double salt is that coordination complex is a molecule or ion in which a central metal atom is bonded to surrounding molecules or ions, called ligands while a double salt is a combination of two different salts that are crystallized together.

Coordination complexes and double salts represent distinct classes of chemical compounds. Each has its unique characteristics and structures.

Key Areas Covered

1. What is a Coordination Complex 
      – Definition, Features, Applications
2. What is a Double Salt
      – Definition, Features, Applications
3. Similarities Between Coordination Complex and Double Salt
      – Outline of Common Features
4. Difference Between Coordination Complex and Double Salt
      – Comparison of Key Differences
5. FAQ: Coordination Complex and Double Salt
      – Frequently Asked Questions

Key Terms

Coordination Complex, Double Salt

Difference Between Coordination Complex and Double Salt  - Comparison Summary

What is a Coordination Complex

Coordination complexes consist of a central metal atom or ion surrounded by ligands, which are molecules or ions that donate electron pairs to the metal. At the core of coordination chemistry lies the concept of coordination numbers, which dictate the number of ligands that can coordinate with a central metal atom or ion. In addition, common coordination numbers include 4, 6, and 8, each yielding distinct geometric arrangements around the central metal. For example, a coordination number of 6 often results in an octahedral geometry, where six ligands surround the metal in a symmetrical manner.

The binding between the metal and ligands in coordination complexes relies on coordination bonds, which can be classified into various types such as sigma bonds, pi bonds, and dative bonds. The nature of these bonds contributes to the stability and reactivity of the complex. Transition metals are frequently involved in coordination complexes due to their ability to exhibit variable oxidation states.

Compare Coordination Complex and Double Salt

Figure 1: Cisplatin is a Coordination Complex of Platinum(II) with Two Chloride and Two Ammonia Ligands

Moreover, ligands in coordination complexes can be categorized as monodentate, bidentate, or polydentate, based on the number of binding sites they offer. Polydentate ligands, often referred to as chelating agents, form particularly stable complexes because they can coordinate with the metal at multiple points. The resulting chelate effect enhances the overall stability and solubility of the complex.

Furthermore, coordination isomers, structural isomers, and stereoisomers are prevalent in coordination complexes, introducing a layer of complexity to their characterization. Isomerism arises due to variations in the spatial arrangement of ligands around the central metal, leading to distinct chemical and physical properties.

Applications of Coordination Complexes

Coordination complexes find applications in a multitude of fields, ranging from catalysis and medicine to materials science. In catalysis, certain coordination complexes act as catalysts in chemical reactions, facilitating the conversion of reactants into products with enhanced efficiency. Moreover, in medicine, metal-containing coordination complexes are popular for their potential as anticancer agents, leveraging the unique reactivity of transition metals to target cancer cells selectively.

What is a Double Salt

Double salts are compounds formed by the combination of two different salts through the process of crystallization. These compounds exhibit unique chemical properties that result from the interaction of their constituent ions. The formation of double salts typically occurs when two different salts crystallize together from a solution. This process is influenced by the solubility of the salts and their affinity for each other’s ions. For example, when a solution containing potassium chloride (KCl) and copper sulfate (CuSO₄) evaporates, the double salt potassium copper sulfate (K₂Cu(SO₄)₂) can form. The key to the formation lies in the shared crystalline structure of the two salts.

The structure of double salts is characterized by the arrangement of ions in a repeating pattern. In the case of potassium copper sulfate, the potassium ions (K⁺) and copper sulfate ions (CuSO₄²⁻) form a three-dimensional lattice. In fact, this lattice structure is distinct from the arrangement of the individual salts, showcasing the unique nature of double salts.

Coordination Complex vs Double Salt

Figure 2: Ferric Ammonium Oxalate

One intriguing aspect of double salt chemistry is the ability of these compounds to undergo dissociation in solution. When dissolved in water, double salts dissociate into their constituent ions, similar to regular salts. This dissociation is reversible. In fact, the equilibrium between the dissolved double salt and its ions is a fundamental aspect of double salt chemistry.

The equilibrium between the double salt and its constituent salts can be described by Le Chatelier’s principle. If external conditions, such as temperature or concentration, are altered, the system will adjust to counteract the change and maintain equilibrium. Moreover, this dynamic behavior contributes to the versatility of double salts in various applications.

Applications of Double Salts

Double salts find applications in diverse fields, including agriculture, medicine, and industry. In agriculture, double salts can be utilized as fertilizers due to their ability to release essential nutrients gradually. For instance, carnallite (KCl⋅MgCl₂⋅6H₂O) is a double salt used as a potassium and magnesium fertilizer.

In medicine, double salts are useful in pharmaceutical formulations. Their controlled release properties can be harnessed to optimize drug delivery, ensuring a steady and prolonged release of active compounds within the body. This controlled release is particularly valuable in managing chronic conditions where a sustained therapeutic effect is desired.

Meanwhile, in industry, double salts play a role in various processes. Alum, a class of double salts, has been historically used in water purification and as a mordant in dyeing processes. Furthermore, the unique chemical properties of double salts make them valuable in specific industrial applications, contributing to their widespread use.

Similarities Between Coordination Complexes and Double Salt

  • Both coordination complexes and double salts contain ions and form through ionic interactions.
  • They exhibit increased structural complexity compared to simpler chemical compounds.
  • Moreover, they tend to dissociate in solution.

Difference Between Coordination Complex and Double Salt


Coordination complexes are compounds in which a central metal atom or ion is bonded to surrounding molecules or ions, known as ligands. Meanwhile, double salts are a combination of two different salts that crystallize together to form a single substance.

Behavior in Solution

Coordination complexes typically remain intact as a single molecular species when dissolved in solution, while double salts dissociate into their constituent salts when dissolved in water, each maintaining its individual chemical identity.


Generally, coordination complexes do not readily dissociate into their individual components under normal conditions. But double salts can be easily separated back into their original salts by dissolving in water and then recovering the individual components through evaporation.

FAQ: Coordination Complex and Double Salt

What is an example of a coordination complex?

An example of a coordination complex is hexaaquo cobalt dichloride, Co(H2O)6Cl2

What are coordination complexes used for?

Coordination complexes are catalysts in technological processes used during organic synthesis,

How are double salts formed?

Double salts are obtained by the combination of two different salts crystallized in the same ionic lattice.


A coordination complex is a molecule or ion in which a central metal atom is bonded to surrounding molecules or ions, called ligands, while a double salt is a combination of two different salts that are crystallized together. Thus, this is the main difference between coordination complex and double salt.


1. “Coordination Complex.” Wikipedia. Wikipedia Foundation.
2. “Double Salt.” Wikipedia. Wikipedia Foundation.

Image Courtesy:

1. “Ferric ammonium oxalate” By W. Oelen(CC BY-SA 3.0) via Commons Wikimedia
2. “Cisplatin-3D-balls” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia

About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

Leave a Reply