Question

Which complex ion geometry has the potential to exhibit cis– trans isomerism: linear, tetrahedral, square planar, octahedral?

Answer 1

Only the square planar and octahedral complexes can exhibit cis-trans isomerism.

Explanation:

Linear and tetrahedral complexes cannot exhibit cis-trans isomerism, but square planar and octahedral complexes can.

Square planar complexes

In the two complexes shown below, one has the two iodine atoms adjacent to each other (cis), and the other has the iodine atoms across from each other (trans)

(from chemwiki.ucdavis.edu)

Octahedral complex ions*

The octahedral tetraamminedichloridocobalt(III) ion, `["Co"("NH"_3)_4"Cl"_2]^+`, shown below can exist as cis and trans isomers.

(from wps.prenhall.com)

The cis isomer has the chlorine atoms (green balls) adjacent to each other, and the trans isomer has them across from each other.