Stereoisomerism in complex ions Flashcards
What are stereoisomers?
Same structural formula but a different arrangement of atoms in space.
What are the 2 types of stereoisomerism that complex ions can display? (2)?
- Cis-trans isomerism.
- Optical isomerism.
For complex ions, what does the type of stereoisomerism depend on? (2)?
- The number and type of ligands that are attached to the central metal ion.
- Shape of the complex.
What complex ions display cis-trans isomerism?
Some four-coordinate and six-coordinate complex ions containing two different monodentate ligands.
What complex ions display both cis-trans isomerism and optical isomerism?
Some six-coordinate complex ions containing monodentate and bidentate ligands.
- Some square planar and some octahderal complex ion shapes.
What does cis-trans isomerism require the presence of? (2)? Differ in complex ions?
- A C=C double bond.
- Lack of rotation of groups attached to the carbon atoms of the C=C double bond.
- Complex ions do not contain C=C double bonds and the shape of the complex holds groups in different orientations about the central metal ion.
What is the simplest example of cis-trans isomerism? Complex ion?
- In four-coordinate square planar complexes that have no more than two identical ligands attached to the central metal ion.
- [Pd(NH3)2Cl2].
How are trans-isomers arranged? Angles?
- The two identical groups are opposite one another.
- The coordinate bonds between the identical ligands are 180 degrees apart.
How are cis-isomers arranged? Angles?
- The two identical groups are adjacent to one another.
- The coordinate bonds between the identical ligands are 90 degrees apart.
What type of octahedral complexes with monodentate ligands display cis-trans isomerism?
Octahedral complexes containing 4 of one type of ligand and 2 of another type of ligand.
What is the example of an octahedral complex with monodentate ligands that display cis-trans isomerism? Colours?
[Co(NH3)4Cl2]^+.
- The cis-isomer is violet.
- The trans-isomer is green.
What does the cis-isomer (violet) of the octahedral complex with monodentate ligands, [Co(NH3)4Cl2]^+, contain? Angle?
The two chloride ligands are adjacent to each other with their coordinate bonds separated by 90 degrees.
What does the trans-isomer (green) of the octahedral complex with monodentate ligands, [Co(NH3)4Cl2]^+, contain? Angle?
The two chloride ligands are at opposite corners of the octahedron, with their coordinate bonds 180 degrees apart.
What other type of octahedral complexes display cis-trans isomerism?
Ones containing bidentate ligands.
What is the example of an octahedral complex with bidentate ligands that display cis-trans isomerism? And the ligand?
- The bidentate ligand:
1,2-diaminoethane, NH2CH2CH2NH2. Each nitrogen atom in H2NCH2CH2NH2 can form a coordinate bonds to the central metal ion. - [Co(NH2CH2CH2NH2)2Cl2]^+.
What does optical isomerism only occur in?
Octahedral complexes containing two or more bidentate ligands.
What are optical isomers?
Also known as enantiomers, are non-superimposable mirror images of each other, like a left hand and right hand.
What is an example of a complex ion displaying optical isomerism?
[Co(NH2CH2CH2NH2)2Cl2]^+.
What type of isomer cannot form optical isomers? Why?
Trans-isomers because as a mirror image it is exactly the same and can be superimposed.
What other type of octahedral complex does optical isomerism only occur in (ligand type)? Example?
- 3 bidentate ligands instead of just 2.
- [Ru(NH2CH2CH2NH2)3]^2+.
