What are the different types of optical isomers seen in coordination compounds? How do you draw optical isomers of coordination compounds?

1 Answer
Feb 23, 2017

Here's what I get.


Monodentate ligands

Complexes with monodentate ligands are classified as C (clockwise) or A (anticlockwise).

An example is the hypothetical complex ion

Complex ion
(From Department of Chemistry, UWI, Mona)

You assign priorities to the ligands per the usual Cahn-Ingold-Prelog rules.

Arrange the complex so the highest-priority ligand is at the top.

Viewing from the top, you look at the ligands in the horizontal plane.

You designate the isomers as C or A according to whether the direction from the highest to the next-highest priority ligand in the plane is clockwise or anticlockwise.

A and C Isomers
(From Department of Chemistry, UWI, Mona)

Our hypothetical complex was the C isomer.

Δ and Λ isomers

Optically active bis- and tris-bidentate complexes are said to have a screw chirality.

(From CSB | SJU Employees Personal Web Sites - College of Saint Benedict)

You arrange them so they look like left- or right-handed screws.

If you must rotate them clockwise to screw them into the paper, they are classified as Delta Δ (right-handed).

If you must rotate them counterclockwise, they are Lambda Λ (left-handed).

An example is the trisoxalatoferrate(III) ion.


You must twist the left-hand image to the left to screw it into the paper, so it is the Λ isomer.

The other image is like a right-hand screw, so it is the Δ isomer.