COURSE CODE: COURSE TITLE: SESSION: SEMESTER: CLASS MEETINGS:

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BOWEN UNIVERSITY, IWO

COLLEGE OF AGRICULTURE, ENGINEERING AND SCIENCES INDUSTRIAL CHEMISTRY PROGRAMME

COURSE CODE: CHM 231

COURSE TITLE: INORGANIC CHEMISTRY I SESSION: 2020/2021 ACADEMIC YEAR SEMESTER: FIRST

CLASS MEETINGS: TIME RANGE DAY VENUE

11 am-1 pm Monday Physical teaching

LECTURER'S DETAILS:

NAME: DR. A.A. OLANREWAJU MOBILE: +2348038078074

E-MAIL: adesoji.olanrewaju@bowen.edu.ng

ROOM/OFFICE NUMBER: CHEMISTRY BUILDING, 1ST FLOOR, RM 20

COURSE DESCRIPTION: CHM 231 3 CREDITS

Course Outline:

-Simple valence theory-Atomic spectra, atomic radii, bond lengths, bond angles and shapes -Chemistry of the first row transition elements, electronic structures and shapes; oxidation states; their colour, paramagnetic and catalytic nature.

-Comparative Chemistry of the following elements:

(a) Ga, In, Ti, (b) Ge, Sn, Pb, (c) As, Sb, Bi, (d) Se, Te, Po. -Introduction to Co-ordination Chemistry: nature of complexes. -Roles of metals in biochemical systems.

-Nuclear Chemistry: Radioactivity, artificial transmutations -The Chemistry of the main group elements

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MODULE 5

UNIT TITLE: Introduction to Coordination Chemistry SUB-UNITS:

- Writing chemical formula of coordination compounds - Isomerism in coordination compounds

OBJECTIVES:

At the end of the lesson, students should be able to:

i) write correctly the chemical formula of coordination compounds ii) define the term isomerism in coordination compounds

iii) state and explain the different types of isomerism in coordination compounds iv) give appropriate examples of isomers belonging to each classification

v) explain optical isomers in relation to enantiomer, chirality, racemic mixture etc.

Writing chemical formula of coordination compounds

It is the reverse of the rules of naming compounds, in that, the central metal

atom/ion of the complex named last is written first in a square bracket.

For example,

*Tetraaquodichlorochromium(III) chloride is written as:

steps: i write the square bracket i.e. []

ii write the correct symbol of the CMA e.g. [Cr]

iii write the symbol of the ligands and their numbers as subscript e.g.

(H

2

O)

4

Cl

2

iv write the counter ion (Cl

-

) outside the square bracket, on the right side,

since the coordination sphere is cationic.

v crosscheck the oxidation state of the CMA by calculation.

vi combine appropriately and the correct chemical formula is

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*

Potassium hexacyanoferrate(II) is written as:

Here, the coordination sphere takes the anionic side of the compound

K

₄

[Fe(CN)

₆

]

*

Tris(ethylenediamine)zinc(II) nitrate is written as:

[Zn(en)

₃

](NO

₃

)

₂

*

Diamminediaquodibromocobalt(III) sulphate is written as:

 Compounds having same chemical formula but different structures are called isomers.  Isomers have the same molecular formula, but their atoms are arranged either in a

different order (structural isomers) or spatial arrangement (stereoisomers).

 Many different types of isomerism occur because of complicated formulas of many coordination compounds, the variety of bond types and the number of shapes possible. These are described below.

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A. STRUCTURAL ISOMERS 1. Ionization Isomerism

This type of isomerism arise due to difference in the position of groups being inside or outside the coordination sphere of the complex.

₃

.

The coordination number (C.N.) of chromium is 6 in all the three cases, the isomers contain

different number of coordinated water molecules.

3. Linkage Isomerism

Linkage isomerism arises in coordination compounds containing ambidentate ligand. For example,

in NO2- the nitrogen as well as oxygen atom can donate their lone pair.

An example to illustrate this type of isomerism is :

[Co(NH

₃

)5(NO

₂

)]

and

[Co(NH

₃

)

₅

(ONO)]

In the first complex, coordination occurs through nitrogen of the NO2 group, while in the second

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4. Coordination isomerism

This type of isomerism is observed in case of compounds in which both, anionic and cationic parts of the coordination compound are complex.

An example is provided by:

[Co(NH

₃

)

₆

][Cr(CN)

₆

]

, in which the NH3 are bound to Co3+ and the CN- to Cr3+

and

[Co(CN)

₆

][Cr(NH

₃

)

₆

]

where the NH3 are bound to Cr3+ and the CN- to Co3+,

both the anionic and cationic parts are complex ions.

B. STEREOISOMERS

5. Geometrical Isomerism

This is observed based on the position of the ligands (same or opposite sides) in orientation to each other.

 It mostly occurs in compounds with square planar and octahedral geometries.  Geometric isomers cannot be interconverted without breaking chemical bonds. There are two forms of this isomerism:

i) Cis- and trans- isomerism For example,

Cis and Trans isomers of Diamminedichloroplatinum(II)

Cis-diamminedichloroplatinum(II) Trans-diamminedichloroplatinum(II)

 cis-Isomers have like groups on the same side

 trans-Isomers have like groups on opposite sides.

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Class work: Give the name of the cis-trans isomers above

ii) Facial(fac-)-meriodional(mer-) isomerism

If the three ligands ‘a’, or ‘b’, all are in the same plane it gives a meridional (mer) isomer. On the other hand, if they are adjacent forming a triangular face of the octahedron it gives a

facial (fac) isomer. For example,

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6. OPTICAL ISOMERISM

Optical isomers – non-superimposable mirror images

• Termed chiral- in form of a molecule or ion that exists as a

pair of enantiomers

• Rotate polarized light in different directions

– Rotation to the right – dextrorotatory (d isomer)

– Rotation to the left – levorotatory (l isomer)

• Enantiomers – a pair of d and l isomers

• Racemic mixture – equimolar mixture of two enantiomers

– Net rotation of polarized light is zero

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*

Chemical example of non-superimposable mirror images

 The left hand molecule cannot be rotated so that it matches exactly the right

hand molecule, and therefore the complex exhibits stereoisomerism.



The two forms are called dextro(d) or laevo (l) depending upon the

direction they rotate the plane of polarized light in a polarimeter (d rotates to

the right, and l to the left).

Optical isomers of geometric isomers

Cis-, rotate in any manner,

Trans-, rotate 90

o

,

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Working Assignment

1. Write the chemical formulae of the following coordination compounds

i) Hexaammineplatinum(IV) chloride

ii) Bis(ethylenediamine)dinitroiron(III) sulphate

iii) Pentacarbonyliron(0)

iv) Sodium tetrahydroxozincate(II)

v) Hexaamminecobalt(III) hexacyanochromate(III)

2. Which class/type of isomerism would the following isomers belong?

i) [Co(NH

3

)

5

Cl

2

]NO

2

and [Co(NH

3

)

5

(Cl)(NO

2

)]Cl.

ii) [Cr(H

2

O)

5

(NCS)] and [Cr(H

2

O)

5