CAIE A-Level Chemistry 28.4 Stereoisomerism in Transition-Metal Complexes

Practise drawing cis/trans and optical isomers of complexes and deducing polarity from three-dimensional symmetry.

Exam points

draw all distinct cis/trans and optical isomers while preserving the complex geometry and ligand denticity
identify enantiomers as non-superimposable mirror images and distinguish them from geometrical isomers
deduce polarity by deciding whether individual bond dipoles cancel in the three-dimensional arrangement

Covered syllabus points

28.4.1—Types of stereoisomerism shown by complexes 28.4.2—The overall polarity of complexes such

[Maximum number: 4]

Titanium is a transition element in Period 4. It is commonly found as $\mathrm{TiO}_{2}$ in minerals.

(a)

Some reactions of $\mathrm{TiO}_{2}$ are shown in Fig. 3.1.

The anion, acac $^{-}$ , is a bidentate ligand.

Fig. 3.1

[ 4 ]

(i)

$\mathrm{Ti}(\mathrm{acac})_{2} \mathrm{C} l_{2}$ shows both optical and geometrical (cis/trans) isomerism.
$\mathrm{Ti}(\mathrm{acac})_{2} \mathrm{C} l_{2}$ exists as three stereoisomers.
The structure of one stereoisomer of $\mathrm{Ti}(\mathrm{acac})_{2} \mathrm{Cl}_{2}$ is shown in Fig. 3.2.