Complexes show structural isomerism and stereoisomerism including geometric and optical forms.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Isomers are compounds with the same formula but different arrangements of atoms. Structural isomers of complexes include ionization isomers, which exchange a ligand with a counter-ion, linkage isomers, in which a ligand such as nitrite binds through different atoms, and coordination isomers in salts containing more than one complex ion. Stereoisomers include geometric isomers, such as cis and trans or fac and mer, and optical isomers, which are non-superimposable mirror images. Isomers can differ in colour, magnetism, reactivity and biological activity. Recognizing isomerism is essential when designing and characterizing coordination compounds.
Key ideas: Count isomers: octahedral MA4B2 gives 2 (cis, trans), MA3B3 gives 2 (fac, mer), square planar MA2B2 gives 2 (cis, trans) while tetrahedral MA2B2 gives none. Chiral examples are [M(en)3] with delta and lambda forms and cis-[MA2B2C2]. Optical isomers rotate plane polarized light in opposite directions. Linkage isomers include nitro versus nitrito.
Common mistakes and connections: Students claim tetrahedral complexes show cis-trans isomerism (they do not), forget to check for a mirror plane when deciding optical activity, or count isomers by drawing the same structure rotated. Trans-[Co(en)2Cl2]+ is achiral but the cis form is chiral. Links to coordination number, stereochemistry, drugs such as cisplatin and symmetry.
Number of stereoisomers: cis and trans forms are possible, while chelated complexes can add optical isomers, as in [Co(en)2Cl2]+. The interactive lesson shows this as a live animation or chart.
cis-Platin is an effective anticancer drug, whereas the trans isomer is inactive.
Complexes show structural isomerism and stereoisomerism including geometric and optical forms.
Isomerism in Complexes is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: Spectrochemical Series, High Spin and Low Spin Complexes, Color of Transition Metal Complexes.
The next topics in Bonding & Molecular Structure are Hydrogen Molecule Ion and Hypervalency.
Yes. The interactive lesson includes a self-check question on Isomerism in Complexes, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Isomerism in Complexes is topic 96 of 104 in Bonding & Molecular Structure.