DIGITAL DIARY
Name – DEBASHISH SEN
KV JHAGRAKHAND
GROUP-07
CHAPTER- CO-ORDINATION COMPOUNDS
SUB TOPIC.
1. Werner’s coordination theory
2. Difference between a double salt and a complex.
3. Definitions of some important terms pertaining to coordination compound
(i)
coordination entity
(ii)
central atom
(iii)
Ligands
(iv)
Coordination number
(v)
Coordination sphere
(vi)
Coordination polyhedron
(vii) Oxidation number of central atom
(viii) Homoleptic and heteroleptic complexes.
DETAILS
WERNER’S COORDINATION THEORY
DOUBLE SALT AND COMPLEX
DEFINITIONS OF SOME IMPORTANT TERMS
coordination entity :-
Central atom/ion
LIGANDS
(d) Coordination number
(e) COORDINATION SPHERE
(f)COORDINATION POLYHEDRON
(g) OXIDATION NUMBER
(I) HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
EVALUATION TOOLS
CONCEPTS
WERNER’S COORDINATION THEORY
POSTULATES:1. In coordination compounds metals show two types of linkages i.e primary and secondary
2. The primary valences are normally ionisable and are satisfied by negative ions.
3. The secondary valence are non ionisable .These are satisfied by neutral molecules or negative ions.
The secondary valence is equal to the coordination number and is fixed for a metal.
4. The ions/groups bound by the secondary linkages to the metal have a characteristic spatial
arrangement corresponding to different coordination number.
DOUBLE SALT AND COMPLEX
Double salt like KCl.MgCl2.6H2O dissociate completely into ions in aqueous solution where as
complex ion s such as [Fe(CN)6]4- of K4[Fe(CN)6] do not dissociate into ions in aqueous solutions.
DEFINITIONS OF SOME IMPORTANT TERMS
coordination entity :An assembly consisting of a central atom (usually metallic) to which is
attached a surrounding array of other groups of atoms (ligands).
For example:- [Ni(CO)4], [PtCl2(NH3)2] etc
Central atom/ion
In a coordination entity, the atom/ion to which a fixed number of ions/groups are bound in a definite
geometrical arrangement around it, is called the central atom or ion. For example, the
central atom/ion in the coordination entities:
[NiCl2(H2O)4], [CoCl(NH3)5]2+ and [Fe(CN)6]3– are Ni2+, Co3+ and Fe3+, respectively.
These central atoms/ions are also referred to as Lewis acids.
LIGANDS
In coordination chemistry, a ligand is an ion, or molecule that binds to a central metal-atom to form a
coordination complex. The bonding between metal and ligand generally involves formal donation of one or
more of the ligand's electron pairs. The metal-ligand bonding can range from covalent to more ionic.
Furthermore, the metal-ligand bond order can range from one to three. Ligands are viewed as Lewis bases,
although rare cases are known involving Lewis acidic "ligands Metal and metalloids are bound to ligands in
virtually all circumstances, although gaseous "naked" metal ions can be generated in high vacuum. Ligands
with one donor atom is called as monodentateligand. Example- CN-, NH3 etc Ligands with two donor atom
is known as bidentate etc.
(d) Coordination number
The coordination number (CN) of a metal ion in a complex can be defined as the number of ligand donor
atoms to which the metal is directly bonded. For example, in the complex ions, [PtCl6]2– and [Ni(NH3)4]2+,
the coordination number of Pt and Ni are 6 and 4 respectively. Similarly, in the complex ions, [Fe(C2O4)3]3–
and [Co(en)3]3+, the coordination number of both, Fe and Co, is 6 because C2O4 and ethylene diamine
Are didentate.
(e) COORDINATION SPHERE
The central atom/ion and the ligands attached to it are enclosed in square bracket and is collectively termed
as the coordination sphere.
(f) COORDINATION POLYHEDRON
The spatial arrangement of the ligand atoms which are directly attached to the central atom/ion defines
coordination polyhedron.
Y(g) OXIDATION NUMBER :- The oxidation number of the central atom in a complex is defined as the
charge it will carry if all the ligands are removed along with their electron pairs that are shared with the
central atom/ion. For example :- [Cu(CN)4]3- the oxidation number is +1 and it is written as Cu(I)
(h) HOMOLEPTIC AND HETEROLEPTIC COMPLEXES:- Complexes in which a metal is bound to
only one kind of donor groups then it is called as homoleptic complex. For example :- [Cu(NH3)4]2+. And
the complex which is bound to different types of ligands are known as heteroleptic complex. For example:[Co(NH3)4Cl2]+.
(B) HOMEWORK :concepts
1. Define ligand.
(Ligands)
2. What are homoleptic complex.
(homoleptic and heteroleptic complex
3. Write down the postulates of Werner’s coordination theory.(Werner’s coordination theory)
4. Give examples for heteroleptic complexes.
(homoleptic and heteroleptic complex)
5. Define ambidentate ligand.
(ligand)
6. Find the oxidation number of Cu in [Cu(CN)6]4-.
(oxidation number)
7. Differentiate between double salt and coordination compound. (Double salt)
8. What is the denticity of EDTA
(ligands)
REMEDIAL MEASURES
ASSIGNMENT
LEVEL 1- FOR SLOW LEARNERS
1. Name the ligands in the following complexes
(a)
[Cu(NH3)4]2+
(b) [Co(NH3)4Cl2]+.
(b) [Cu(CN)6]42. Give two examples each of double salt and complex.
3. Identify the ambidentate ligand
(i)
[Co(CN)6]3(ii) [Cu(NH3)4]2+
(iii) [Cr(NC)6]4LEVEL 2 –FOR AVERAGE STUDENTS
1. What is denticity.
2. Define chelate.
3. Give the structure of EDTA.
4. Explain the bonding in coordination compounds of Werner’s postulates.
5. Give one example each of monodentate, bidentate and hexadentate ligand.
LEVEL 3-FOR BRIGHT STUDENTS
1. Find out the primary and secondary valencies of following compounds
(i)
[Co(en)3]3+
(ii)
[Cu(NH3)4Cl2]
2. FeSO4 solution mixed with (NH4)2SO4 solution in 1:1 molar ratio gives the test of Fe2+ ion but
CuSO4 solution mixed with aqueous ammonia in 1:4 molar ratio does not give the test of Cu2+ ion
.Explain why?
PROJECT
Collect some salts from chemistry laboratory and find out whether they are double salt or complex.
If complex then name the ligands present in the complex and find out their primary and secondary
valencies.