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Some compounds, such as coordinates, have the same formula as one another yet have different properties and a different structural design. Despite the fact that they use the same formula, they have different colors. You might be wondering what these compounds are. Let me tell you. Would you please continue reading the section below to learn more about isomerism and coordination compounds, which is a fascinating topic in itself?
Ligands: Coordination isomerism
A metal ion can’t exist in isolation in solution. Instead, it must join with ligands such as solvents or simple ions to form complex ions or coordination compounds to function. The presence of a central atom or ion, which is typically a transition metal, distinguishes these complexes from their counterparts.
It is common for ligands to form coordinate bonds with one another and one or more central metal atoms or ions in these complexes; however, this is not the case in all complexes. Lewis bases (electron-pair donors) and Lewis acids (electron-pair acceptors) are two different types of ligands (electron-pair acceptors).
Compounds with the same chemical composition but different structural formulas are widespread. Isomers of coordination compounds Coordination molecules exhibit a wide range of isomorphisms. The following is a short summary of some of the most common types.
The two types of isomerism in coordination compounds are as follows:
- Stereo Isomerism
- Structure Isomerism
Structural Isomers: Coordination Isomerism
When two or more structural isomers have the exact chemical formula but differ in the bonding patterns and atomic organization, they are said to be structural isomers. The following are the subcategories of structural isomerism:
Linkage Isomers
The term “linkage isomers” refers to two or more coordination compounds in which at least one of the ligands has a distinct donor atom. This sort of isomerism exists exclusively in compounds that contain a ligand capable of binding to the metal atom in two (or more) distinct ways. Linkage isomerism arises when Ambidentate ligands coordinate in several ways. Another Ambidentate ligand is thiocyanate, SCN, which can connect to either the sulfur or nitrogen atoms. These chemicals exhibit linkage isomerism.
coordination isomerism example: [Co(NH3)5(NO2)]2+
Coordination Isomerism
When a metal cation and an anion interact with each other, coordination isomers are formed. Coordination isomers are coordination salts in which the metal cation and anion exchange ligands.
Coordination isomers can be found in pairs in the following situations:
- Zn(NH₃)₄²⁺ CuCl₄²⁻ and Cu(NH₃)₄²⁺ ZnCl₄²⁻
- Co(NH₃)₆³⁺ Cr(CN)₆³⁻ and Cr(NH₃)₆³⁺ Co(CN)₆³⁻
Ionisation Isomers
Ionisation isomers are compounds that produce various ions in solution despite having the same composition. This trait, known as ionisation isomerism, is found in compounds that produce different ions in solution.
Pentaamminenitrocobalt sulfate, [CoBr(NH3)5]SO4, and Pentaammine Sulphato Cobalt bromide, [Co(SO4)(NH3)5]Br, are two compounds that exhibit this property. In the former, the bromide ion is coupled to the cobalt(3+) ion, while the sulfate ion is located outside the coordination sphere; in the latter, the sulfate ion is located within the coordination sphere while the bromide ion is located outside.
Solvate Isomers
Solvate isomerism refers to isomers that share the same chemical composition but differ in the number of solvent ligand molecules and the crystal lattice counter ion.
For instance, [Cr(H2O)6]Cl3 is a violet liquid, [CrCl(H2O)5]Cl2H2O is a blue-green liquid, and [CrCl2(H2O)4]Cl2H2O is a dark green liquid.
They are distinguished by the fact that one ion is directly connected to the core metal while the other is not. A very similar sort of isomerism occurs when a coordinating group is replaced by a solvent molecule (Solvate Isomerism). This is referred to as Hydrate isomerism in the case of water.
Stereoisomers
Stereoisomers are composed of identical atoms and bonds that differ only in their relative orientation. They are classified into the following categories:
Geometrical Isomers
Geometrical Isomerism is a sort of stereoisomerism in which the molecular formula and structure are the same, but the relative arrangement of atoms differs. Geometrical Isomerism is a common occurrence in heteroleptic compounds. This sort of Isomerism occurs due to the ligand’s various geometric configurations.
Coordination Isomerism Example
- But-2-ene – The CH3 groups are on opposing sides of the double bond in one example and on the same side in the other.
Optical Isomerism
Optical isomers are two compounds with the same type and amount of atoms and bonds (i.e., the connectivity between atoms is identical). Still, they have different spatial arrangements of the atoms. Each structure with a non-superimposable mirror image is referred to as an enantiomer. Chiral molecules or ions are those that exist as optical isomers.
Conclusion
For the development of coordination compounds, molecules with the same formula but various ligand configurations were essential. Isomers are compounds with the same formula but distinct atom configurations. So, coordination compounds have isomers like organic compounds, as well as certain unique isomers. Isomers are compounds having the same molecular formula but distinct structural formulae. Stereoisomers, enantiomers, and geometrical isomers are among the various isomers. It is mainly divided into structural and stereoisomeric isomerism.
