This document discusses coordination chemistry concepts including different types of salts such as simple salts, double salts, and complex salts. It defines coordination compounds and complex ions, and describes Werner's coordination theory which proposed that metals have primary and secondary valences. Ligands are defined as electron-rich species that bond to metals. Different classifications of ligands and coordination numbers are provided. The coordination sphere and effective atomic number concept are also summarized.

1. SANSKRITI
COLLEGE
DEPARTMENT OF CHEMISTRY

2. COORDINATION
CHEMISTRY
DR. G K SINGHAL
PROFESSOR
DEPARTMENT OF CHEMISTRY
(SANSKRITI COLLEGE JAIPUR )
NISHANT KATARA
STUDENT
B.SC. CHEMISTRY (H)

3. INTRODUCTION
 Salt – Three type
1. simple salt
2. double salt
3. complex salt

4. SIMPLE SALT
 The simple salt is generally formed by the
neutralization of acid and alkali.
 Eg. Formation of NaCl -
NaCl is formed by the reaction of HCl and
NaOH .
 These simple salts ionise when they dissovled
in water.
 Eg. KCl, NiCl , etc.

5. DOUBLE SALT
 When two or more simple salt solutions are
mixed in requisite proposition and allowed to
crystaline together, addition or molecular
compounds are formed. These compounds
are either double salt or coordination
compound.
 Double salt or lattice compound exist only in
the crystalline state and ionise into water or
any other solvent.

6. Example – double salt
 KCl + MgCl2 = KCl. MgCl2.6H2O (carnallite)
 Alum – M2`(SO4).M2```(SO4)3.24 H2O
 these compound are stable in solid state and
decompose or ionise in water or any solvent

7. COMPLEX SALT
 A complex salt is a salt which contains a
complex ion or complex neutral molecule in
which there is a central metal ion surrounded
by a number of neutral molecules or negative
ions.
 Examples:
potassium ferrocyanide (K4[Fe(CN)6]),
potassium argento cyanide (K [Ag(CN)2]) ,
tetra amino cupric sulphate ([Cu(NH3)4]SO4)
etc.

8. COMPLEX ION
 It may be defined as an electrically charged
radical which is formed by the combination of
a central metal atom or ion surrounded by a
group of ions or neutral molecule.
 Eg. - [Fe(CN)6]-4
[Cu(NH3)4]+2

9.  Rossotti (1961)defined the complex ion – as a
species formed by the association of two or
more simpler species each capable of
independent existence.
 When one of the simpler species is a metal ion
, the resulting entity is known as a metal
complex .

10. COORDINATION COMPOUND
 It may be also defined as – a compound that
results from the combination of two or more
stable chemical species and retains its identity
in solid as well as dissolved state.
 Eg. K4[Fe(CN)6],
K3[Fe(CN)6] etc

11. CLASSIFICATION OF COORDINATION
COMPOUND
1. Blitz`s classification – according to Blitz
(1927),
A)-normal complex – normal complex are those
which are reversibly dissociated in solution to
their components.
[Cd(CN)4]-2 Cd+2 + 4CN-
such complexes are also known as ionic
complexes.

12.  B)- penetration complexes-
those compound /ions which possess sufficient
stability to retain their identity in solution , are
called as penetration complexes.
they are not reversibly dissociated in solution
like normal complexes.
Such complexes are also known as covalent
complexes.
Eg. [Cu(CN)4]-3 Cu+ + 4CN-

13. 2. Second method of classification –
Based on nature of the ligand.
3. Third method of classification –
Based on character in solid and in
solution state.
4. Fourth method of classification -
Based upon the electronic
configuration of the central metal atom or ion.

14. WERNER`S THEORY OF CO-
ORDINATION
 Father of modern co-ordination chemistry-
Alfred Warner
(1893)
 To explain the formation of complex compound
, Werner give a theory known as Werner co-
ordination theory.
 According to this theory – 4 postulate
1. Valency 2. satisfaction 3. variation
4.direction

15. VALENCY
 The metals possess two type of valency –
1. Primary Valencies
2. Secondary Valencies
 In mordern terminology
(i) Corresponds to oxidation state
(ii) To coordination number

16. SATISFACTION
 Primary valency are satisfied with anion ,
resulting in the formation of ionic compound.
Also termed as oxidation state of metal.
 Secondary valency also known as
coordination number are satisfied with L.P.
donor species , known as ligand.

17. VARIATION
 Primary valency are variable
eg . Ferus , ferric
 Secondary valency or C.N. of the metal is fixed
for a particular oxidation state.

18. DIRECTION
 Primary valency is non directional.
 Secondary valency is directional.

19. LIGAND
 The electron rich species, which may be
charged species, e.g. Cl-, CN-, NO2-, etc
orneutral species e.g. H2O, NH3,
NH2CH2C2NH2, CO, NO, etc., that can
donate anelectron pair to the metal atom/ion
are called ligands.
 Types of ligands- The ligands can be
classified in the following ways-

20. TYPE I- Based on electron
accepter/donor properties of the ligand
 σ (sigma) donor ligands are those ligands which
can only donate electron pair to the meal ion, e.g.
H2o , NH3 ,F-. these ligands are also known as
weak field ligands.
 σ (sigma) donor and Π (pi) accepter ligands
are those ligands which can donate electron pair
and also have a tendency to accept electron in
their empty antibonding π molecular orbitals (MO).
Such ligands can involve in backbonding (π bond)
with the metal ion. For example, CO, CN-, NO,
etc. These ligands are also known as strong field
ligands.

21.  Π (pi) donor ligands Are those ligands like
benzene and ethylene,which do not have lone
pair of electrons but only π electrons
fordonation to the metal atom/ion.

22. Type II- Based on the basis of number of
donor atoms in the ligand
 Monodentate or unidentate ligands-
The ligands that bound to a metal ion through a
single donor atom are called as monodentate
or unidentate ligands, e.g. H2o , NH3 ,cl-
These ligands can be further divided into the
following subclasses on basis of charge.
1. Neutral – H2o , NH3 , NO , CO
2. Negative - Cl- , I- , CN-, SCN-
3. Positive - NO+ , NH2NH3
+

23.  Ambidentate ligands -
Some ligands have two or more than two different
donor atoms. These ligands can attach through
any of the donor atoms.
 They are given different names depending upon
nature of the donor atom linked to the metal atom.
These ligands are known as ambidentate ligands.
 e.g. NO2(donor atom may be either N or O),
SCN- (donor atom may be either S or N),
CN- (donor atom may be either C or N),
S2O3-2 (donor atom may be either S or N).

24.  Polydentate (bidentate, tridentate,
tetradentate, pentadentate,hexadentate)
ligands
 These ligands bind to a metal atom/ion
through two, three, four, five and six donor
atoms, respectively. These ligands are also
known as chelating ligands.
 These ligands form ring type (chelates)
compounds.

25. POLYDENTATE LIGANDS

26. Type III- Based on size of
ligand
 Chelating ligands are those ligands that
bind via more than one atom and form
chelate complexes (ring complexes). These
complexes are more stable than complexes
formed from monodentate ligands. The
enhanced stability is known as the chelate
effect.

27.  Macrocyclic ligands are the chelating ligands
that can form a large ring and surround the central
atom or ion partially or fully and bond to it. The
central atom or ion resides at the centre of the
large ring. This complex formed is more rigid and
inert as compared to the chelate compound and is
known as macrocyclic complex.
 Heme is a macrocyclic complex in which the
central iron atom is present at the centre of a
porphyrin macrocyclic ring. Dimethylglyoximate
complex of nickel is a synthetic macrocycle
formed from the reaction of nickel ion with
dimethylglyoxime in ammonical medium.

28. Nickel(II) bisdimethyl
glyoximate

29.  The order of ligands to form stable
compounds-
Macrocyclic > Chelate > Monodentate

30. Type IV- Based on their use in
reactions
 Actor ligands are those ligands which take
part in chemical reaction.
 Spectator ligands are tightly coordinating
polydentate liangds which do not take part in a
chemical reaction. Phosphines, allyl groups in
catalysis, trispyrazolylborates (Tp),
cyclopentadienyl ligands (Cp) and many
chelating diphosphines such as 1,2-
bis(diphenylphosphino) ethane ligands (dppe)
are spectator ligands.

31. COORDINATION NUMBER
(CN)
 The coordination number of a metal atom/ion is
the number of ligands attached to it in a complex
compound. Coordination number may be two,
three, four, five, six, seven, eight, nine or even
higher in case of lanthanides and actinides
Coordination number depends on size, charge
and electronic configuration and nature of
meal/ion and ligands.
 large metal atoms show high CN
 bulky ligands reduce coordination number
 Lewis bases easily donate electrons to metals and
metals with lesser number of electrons can easily
accept electrons.

34. Co-ordination sphere
 The coordination sphere of a coordination
compound comprises the central metal
atom/ion and ligands attached to it. The
coordination sphere is enclosed in brackets [ ].
 The ions excluding the coordination sphere
are called as counter ions.
 K+[Fe(CN)6]-4
Here K+ -counter ion
[Fe(CN)6]-4 - coordination sphere

35. EFFECTIVE ATOMIC NUMBER
CONCEPT
 This rule is given by English Chemist Nevil V.
Sidgwick.
 Effective atomic number (EAN) is the total
number of electrons in metal atom/ion (atomic
number) plus the electrons gained from
ligands.
 This EAN is the atomic number of a noble gas.
 Therefore, EAN decides stability of
coordination compound. If a coordination
compound follow EAN rule, than it is stable
one.

36.  EAN= Atomic number of metal atom/ion +
number of e- donated by ligands or 2 x number
of ligands (as each ligand can donate two
electrons to metal atom/ion).
 For [Co(NH3)6]+3
Atomic number of Co=27; Atomic number of Co+3
=24; there are six ligands hence electrons donated by
6 ligands = 6 x 2
EAN = 24 + (6 x 2) = 36 (atomic number of Krypton;
Kr)

37. THANK YOU
Department of chemistry
Sanskriti college , Jaipur
www. Sanskriticoolege.org