Stereoisomerism in complexes
| English | Chinese | Pinyin |
|---|---|---|
| stereoisomerism | 立体异构 | lì tǐ yì gòu |
| square planar | 平面正方形 | píng miàn zhèng fāng xíng |
| octahedral | 八面体形 | bā miàn tǐ xíng |
| optical isomerism | 旋光异构 | xuán guāng yì gòu |
| bidentate | 双齿 | shuāng chǐ |
Isomers around a metal
- Complexes can show stereoisomerism 立体异构 — same bonds, different 3-D arrangement.
- Two kinds: geometrical and optical.
- It can even change the complex's polarity.
Complex stereoisomer lab
Classify complex isomers by ligand arrangement.
Transition-metal complexes can show both geometrical and optical isomerism.
Square planar/octahedral complexes show cis/trans; octahedral ones with bidentate ligands show optical isomerism.
Octahedral complexes with two different ligand types can show cis-trans isomerism.
A form of stereoisomerism in complexes.
Geometrical (cis/trans)
- Appears in square planar 平面正方形 complexes (e.g. $[\text{Pt}(\text{NH}_3)_2\text{Cl}_2]$) and octahedral 八面体形 ones.
- The two identical ligands are adjacent (cis) or opposite (trans).
Cis and trans isomers of a square planar complex
Geometrical (cis/trans) isomerism in [Pt(NH₃)₂Cl₂] means the two identical ligands are:
In a square planar complex the matching ligands sit next to each other (cis) or across (trans).
Match each isomerism idea in complexes.
Each item links the term to its correct meaning.
Optical isomerism 旋光异构
- Appears in octahedral complexes with bidentate 双齿 ligands, e.g. $[\text{Ni}(\text{en})_3]^{2+}$.
- It has two non-superimposable mirror images.
- Polarity: a cis form may be polar, while the trans form is often non-polar (its dipoles cancel).
Optical isomerism appears in octahedral complexes that have:
Octahedral complexes with bidentate ligands can exist as two non-superimposable mirror images.
Compared with a cis complex, the matching trans complex is often:
In the trans form the opposite ligands' dipoles cancel, so it is often non-polar.
Where isomerism appears
- Cis-trans isomerism occurs in octahedral and square-planar complexes with two ligand types.
- Some octahedral complexes also show optical isomerism.
You've got it
- geometrical (cis/trans): in square planar ([Pt(NH₃)₂Cl₂]) and octahedral complexes — ligands adjacent (cis) or opposite (trans)
- optical: in octahedral complexes with bidentate ligands (e.g. [Ni(en)₃]²⁺) — mirror images
- a cis complex may be polar; the trans form is often non-polar