Transition Metals - Cis-Trans Isomerism in Complex Ions (A-Level Chemistry)
Cis-Trans Isomerism in Complex Ions
Geometric Isomerism in Complex Ions
In organic molecules, such as transition metals, geometric isomers are compounds with the same molecular formula but different arrangement of their atoms in space.
Transition metal complexes can show both
- Cis-trans isomerism – Occurs in both square planar and octahedral monodentate complexes.
- Optical isomerism – Only occurs in octahedral complexes. We will look at this in the next tutorial.
Cis-Trans Isomerism
Cis-Trans Isomerism: Octahedral Monodentate Complexes
In cis-trans isomerism, the octahedral complex must have two different types of monodentate ligands.
The ligands are in a different position relative to one another.
Example: CoCl₂(H₂O)₄
This octahedral complex ion in the diagram above, has two types of ligands, chloride and water molecules. Depending on the position of the chloride ions we can get:
- Trans isomer – Occurs when the chloride ions are at opposite ends of
the complex. - Cis isomer – If the chloride ions are on the same side of the complex
Cis-Trans Isomerism: Square Planar Complexes
Cis-trans isomerism occurs in square planar complexes with two different pairs of ligands.
- Trans isomer – Occurs when the pairs are opposite to each other.
- Cis isomer – Occurs when the pairs are adjacent to each other.
Example: Pt(NH₃)₂(Cl₂)
The diagram shows the square planar complex called platin.
The first diagram shows the chloride ions are opposite each other. This is the trans-platin isomer
The second shows the chloride ions are adjacent to each other, so this is the cis-platin isomer.
Cis-platin, cis-[Pt(NH₃)₂(Cl₂)], is commonly used as an anti-cancer drug. The symmetry of the cis-complex allows it to bind to the DNA strand. This makes it difficult for the DNA strand in cancer cells to replicate so they die.
Trans-platin is unable to do this and is ineffective in cancer treatment.
Transition metals are a group of elements located in the middle of the periodic table, characterized by having partly filled d orbitals in their outer electron shell. They are known for their unique properties and are used in a wide range of applications, including electronics, medicine, and construction.
Cis-Trans Isomerism, also known as geometric isomerism, refers to the arrangement of atoms in a molecule in which the same atoms are bonded to each other but have different arrangements in space. This can result in two or more different isomers with different physical and chemical properties.
Cis-Trans Isomerism in complex ions refers to the arrangement of atoms in complex ions, which are formed by transition metals and their ligands. In these ions, the ligands can have different arrangements in space, resulting in two or more different isomers with different physical and chemical properties.
Transition metals are known for exhibiting Cis-Trans Isomerism because of the way they form complex ions with ligands. The presence of partially filled d orbitals in the outer electron shell of transition metals allows them to form complex ions with different arrangements of ligands, resulting in Cis-Trans Isomerism.
Ligands are molecules or ions that bond to a central metal ion to form a complex ion. They are typically Lewis bases, meaning they have an unshared electron pair that can bond to the metal ion.
Cis-Trans Isomerism affects the properties of complex ions by changing the arrangement of ligands in space. This can result in different physical and chemical properties, such as different colors, magnetic properties, and reactivity.
Some real-world applications of Cis-Trans Isomerism in complex ions include their use in the production of dyes, pigments, and pharmaceuticals. The different isomers can have different colors and reactivity, making them useful in these industries.
The study of Cis-Trans Isomerism in complex ions is relevant to A-Level Chemistry students because it provides a deeper understanding of the properties and reactivity of transition metals and their complex ions. It also introduces students to the real-world applications of these ions and the impact they have on industries such as the production of dyes, pigments, and pharmaceuticals.
Some challenges associated with the study of Cis-Trans Isomerism in complex ions include the complexity of the structures and the difficulty in determining the arrangement of ligands in space. Additionally, the different isomers can be difficult to isolate and study, making it challenging to determine their physical and chemical properties.
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