(a)

The $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]$ complex shows stereoisomerism.

Complete the three-dimensional diagrams to show the two isomers of $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]$ .
Suggest the type of stereoisomerism.

type of stereoisomerism

[ 2 ]

[Maximum number: 4]

Transition elements are important metals because of their characteristic properties.

(a)

The $\left[\mathrm{CrCl}_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{+}$ complex ion shows stereoisomerism.

[ 4 ]

(i)

Name this type of stereoisomerism.

[ 1 ]

(ii)

Draw three-dimensional diagrams to show the two stereoisomers of $\left[\mathrm{CrCl}{ }_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{+}$ .

[ 3 ]

[Maximum number: 4]

Copper is a transition element and has atomic number 29.

(a)

Nickel forms the complex ion $\left[\mathrm{Ni}(e n)_{3}\right]^{2+}$ in which it is surrounded octahedrally by six nitrogen atoms.

[ 4 ]

(i)

Name the type of stereoisomerism displayed by $\left[\mathrm{Ni}(e n)_{3}\right]^{2+}$ .

[ 1 ]

(ii)

Draw three-dimensional diagrams to show the two stereoisomers of $\left[\mathrm{Ni}(e n)_{3}\right]^{2+}$ .

[ 3 ]

[Maximum number: 2]

Iron is a transition element in the fourth period. Iron forms compounds containing the ions $\mathrm{Fe}^{2+}$ and $\mathrm{Fe}^{3+}$ .

(a)

E is a complex ion, $\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2} \mathrm{C} l_{2}\right]^{4-}$ , containing $\mathrm{Fe}^{2+}$ with a coordination number of 6 .

[ 2 ]

(i)

E shows both optical isomerism and cis-trans isomerism.

One isomer of E is shown. The $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ ion is represented as

$\mathrm{ox}^{-}$ .

In the boxes, draw three-dimensional diagrams to show:
- the trans isomer of E
- the optical isomer of E.

[ 2 ]

(a)

NO reacts with iron pentacarbonyl, $\mathrm{Fe}(\mathrm{CO})_{5}$ , as shown. NO and CO are both monodentate ligands.

\mathrm{Fe}(\mathrm{CO})_{5}+2 \mathrm{NO} \rightarrow \mathrm{Fe}(\mathrm{CO})_{2}(\mathrm{NO})_{2}+3 \mathrm{CO}

During this reaction the co-ordination number of the iron changes.

[ 1 ]

(i)

Only one stereoisomer of $\mathrm{Fe}(\mathrm{CO})_{2}(\mathrm{NO})_{2}$ exists.

Use this information to suggest the geometry of the complex.

[ 1 ]

(b)

The complex $\mathrm{Ru}(\mathrm{NO}) \mathrm{L}_{2} \mathrm{Cl}_{3}$ exists in three isomeric forms. L represents the monodentate ligand $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{P}\left(\mathrm{CH}_{3}\right)_{2}$ .

[ 3 ]

(i)

Complete the three-dimensional diagrams to show the three isomers of $\mathrm{Ru}(\mathrm{NO}) \mathrm{L}_{2} \mathrm{Cl}_{3}$ .

[ 2 ]

(ii)

Suggest the type of isomerism shown.

[ 1 ]

(a)

There are two isomers with the formula $\mathrm{Ni}\left(\mathrm{R}_{3} \mathrm{P}\right)_{2} \mathrm{I}_{2}$ , but only one structure with the formula $\mathrm{Co}\left(\mathrm{R}_{3} \mathrm{P}\right)_{2} \mathrm{I}_{2}$ . $\left(\mathrm{R}=\right.$ alkyl, $\mathrm{R}_{3} \mathrm{P}$ is a monodentate ligand)

Draw diagrams showing the structure of $\mathrm{Co}\left(\mathrm{R}_{3} \mathrm{P}\right)_{2} \mathrm{I}_{2}$ and the two isomers of $\mathrm{Ni}\left(\mathrm{R}_{3} \mathrm{P}\right)_{2} \mathrm{I}_{2}$ .
$\mathrm{Ni}\left(\mathrm{R}_{3} \mathrm{P}\right)_{2} \mathrm{I}_{2}$

[ 3 ]

(a)

The ethanedioate ion, $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ , can act as a bidentate ligand.

[ 3 ]

(i)

The complex $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right) \mathrm{BrCl}\right]^{-}$ exists as stereoisomers.

Complete the three-dimensional diagrams in Fig. 2.2 to show four stereoisomers of $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right) \mathrm{BrCl}\right]^{-}$ .

The $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ ligand is represented using

.

Fig. 2.2

[ 3 ]

(a)

(i)

$\mathrm{Cu}^{2+}$ ions and en form the complex ion $\left[\mathrm{Cu}(e n)_{3}\right]^{2+}$ .

Draw the two optical isomers of this complex ion.
You may use $\underset{\mathrm{N}}{\mathrm{N}}$ to represent en.

[ 2 ]

[Maximum number: 7]

The ions of transition elements form complexes by reacting with ligands.

(a)

(i)

Platinum forms square-planar complexes, in which all four ligands lie in the same plane as the Pt atom.
There are two isomeric complexes with the formula $\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}$ .
Suggest the structures of the two isomers, and, by comparison with a similar type of isomerism in organic chemistry, suggest the type of isomerism shown here.

Structures of isomers:
isomer 1
isomer 2

Type of isomerism:

[ 7 ]

(a)

Some transition element complexes can show stereoisomerism.
State two types of stereoisomerism shown by transition element complexes.
1
2

[ 1 ]

(b)

The complex $\left[\mathrm{Cr}(e n)_{3}\right]^{2+}$ exists as two stereoisomers whereas the complex $\left[\mathrm{Cr}\left(\mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}\right]^{-}$ exists as four stereoisomers.

Complete the three-dimensional diagrams in Fig. 2.1 to show the four stereoisomers of $\left[\mathrm{Cr}\left(\mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}\right]^{-}$ .

Represent the ligand $-\mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}$ by using $\overbrace{\mathrm{O}}$ .

Fig. 2.1

[ 3 ]