Co-ordination Chemistry, Class 12 Chemistry

1. Co-ordination
Chemistry
• Presented By:
• Mukesh Pareek

2. Co-ordination Compound
Coordination compounds:
The compound which consist of central metal atom or ion, surrounded by
ions or molecules are called as coordination compounds.
Coordination entity:
A coordination entity constitutes a central metal atom or ion bonded to a
fixed number of ions or molecules.
e.g., [CoCl3(NH3)3], [Ni(CO)4], [PtCl2(NH3)2], [Fe(CN)6]4–, [Co(NH3)6]3+.
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. [NiCl2(H2O)4],
These central atoms/ions are Lewis Acid.

3. Co-ordination Compound
Coordination compounds:
The compound which consist of central metal atom or ion, surrounded by
ions or molecules are called as coordination compounds.
Coordination entity:
A coordination entity constitutes a central metal atom or ion bonded to a
fixed number of ions or molecules.
e.g., [CoCl3(NH3)3], [Ni(CO)4], [PtCl2(NH3)2], [Fe(CN)6]4–, [Co(NH3)6]3+.
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. [NiCl2(H2O)4],
These central atoms/ions are Lewis Acid.

4. Co-ordination Compound
Ligand:
The atoms or molecules which surrounding the central metal atom or ion in
a coordination compound, is called Ligand.
Ligands are Lewis Base.
Frame of Coordination of compound:
Ligands are attached to central metal atoms or ions through co-ordinate
bond. Ligand share their lone pair of electron to Metal atom/ion and form a
co-ordinate bond.
Ligands are Lewis Base (e- pair donor) and Metal is Lewis Acid (e- pair
acceptor). L:M:L

5. Co-ordination Compound
Based on e- pair donor atoms ligand are
classified into four types.
1. Monodentate Ligand
2. Bidentate Ligand
3. Polydentate Ligand
4. Ambidentate Ligand

6. Classification of Ligand
2. Bidentate Ligand:
The ligand which consist of two donor atom linked to central metal
atom/ion is called Bidentate Ligand.
e.g., Ethylene diamine NH2-CH2-CH2-NH2
1. Mono/Unidentate Ligand:
The ligand which consist of single donor atom linked to central metal
atom/ion is called Monodentate or Unidentate Ligand.
e.g., Cl- , CN- , OH-,

7. Classification of Ligand
4. Ambidentate Ligand:
The ligand which consist of two different donor atoms and uses the e- pair
either of the two ligates in the complex is called ambidentate ligand.
e.g., MNO2, MSCNMNCS
3. Polydentate Ligand:
The ligand which consist of more then two donor atom linked to central
metal atom/ion is called Polydentate Ligand.
e.g., EDTA

8. Coordination sphere:
The square bracket in which metal is linked to ligands, are called as coordination
sphere. .
The term used in Co-ordination Compound
Coordination
sphere

9. Counter Ion:
The ionizable group present outside the coordination sphere is called Counter ion.
The term used in Co-ordination Compound

10. Charge number:
The net charge residing on the complex ion is called as charge number.
The term used in Co-ordination Compound
[Co(NH3)6]-3
[Fe(CN)6]+2
[Pt(en)2]-1
[Zn(en)F2]

11. Oxidation number of Metal:
The charge carrying by the metal ion in co-ordination compound is called as
Oxidation number of metal.
The term used in Co-ordination Compound
First Remember Ligand charge number
-1 charge ligand
Cl-, F-, Br-, I-, CN-,
Zero charge ligand
NH3, (en), H2O
-4 charge ligand
EDTA
+1 charge ligand
Na+, K+, Li+, H+, Rb+, Cs+
+2 charge ligand
Be+2, Mg+2, Ca+2,

12. Oxidation number of Metal:
The charge carrying by the metal ion in co-ordination compound is called as
Oxidation number of metal.
The term used in Co-ordination Compound
How to find oxidation number of central metal atom/ion?
Firstly, you understand that charge on coordination sphere is charge number but not Metal charge.
Oxidation number means what charge carry by central metal atom/ion in the coordination sphere.
K4[Fe(CN)6] Fe Oxidation Number=?
Let assume Fe oxidation number is X then
+4+X+(-1)6=0
X+4-6=0
X=+2

13. Oxidation number of Metal:
The charge carrying by the metal ion in co-ordination compound is called as
Oxidation number of metal.
The term used in Co-ordination Compound
Formula O.N.
[Co(NH3)6]Cl3 +3
[Cu(NH3)4(H2O)2]Cl2
K3[CoF6]
Cr(CO)6
Cu2[Fe(CN)6]
K[AuCl4]
[Pt(NH3)6]Cl4
Find the Oxidation number of following.

14. Coordination number:
The number of ligand donor atoms, directly attached to central metal atom/ion, is
called Coordination number.
The term used in Co-ordination Compound
Firstly, Remember of Ligand type in your mind:
Monodentate ligand F-, Cl-, I-, Br-, OH-, CN-,NH2-, H2O, NH3
Bidentate ligand (en), C2O4,
Hexadentate ligand EDTA
K4[Fe(CN)6] What is the O.N. of Fe?
Lets assume Fe O.N. is X then
X+(1)6
X=6

15. Find the Coordination number of following
The term used in Co-ordination Compound
Formula Coordination No.
[Co(NH3)6]Cl3
[Cu(NH3)4(H2O)2]Cl2
K3[CoF6]
[Co(en)2Br2]2SO4
Cu2[Fe(CN)6]
K[AuCl4]
[Pt(NH3)6]Cl4

16. Oxidation number of central atom
The oxidation number of the central atom in a complex is defined as the charge it
would carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. The oxidation number is represented by a Roman
numeral in parenthesis following the name of the coordination entity.
[Cu(CN)4]3–
[Co(NH3)4Cl2]+
[Co(NH3)6]3+
[CoCl(NH3)5]2+
[CoCl2(NH3)4]+
Co-ordination Compound
X+(-1)4=-3 X=+1

17. Co-ordination Compound
Double Salts Coordination Complex
A double salt dissociate in
water completely into ions.
A coordination complex
dissociate in water with at
least one complex ion
Fe(NH4)2SO4.6H2O
 Fe+2 + 2(SO4)-2 + NH4+
K4[Fe(CN)6]
 K+ +[Fe(CN)6]-4

18. Werner’s Theory of Co-ordination compound:
• The metal in a co-ordination complex, shows two types valences.
[A] Primary Valency [B] Secondary Valency
• Primary Valency is ionizable and satisfied generally by anions.
• Secondary valency is non-ionizable and satisfied by anion & neutral ligand.
• Secondary Valency shows a fixed geometrical/spatial arrangement around
the central metal in a complex.
Co-ordination Compound
Secondary Valency
Primary Valency
Ionizable
Non-ionizable

19. Example Primary Valency Secondary
Valency
[Co(NH3)6]Cl3
3 6
[Fe(CO)5] 0 5
[Mn(Cl)6]-4 0 6
[Pt(NH3)6]Cl4
[Pt(NH3)5Cl]Cl3
[Pt(NH3)4Cl2]Cl2
[Pt(NH3)3Cl3]Cl
AgNO3
4 Mole of AgCl
3 Mole of AgCl
2 Mole of AgCl
1 Mole of AgCl

20. Structure of Complex
Based on the Co-ordination number of complex
C.N. = 4
C.N. = 6
Octahedral
Tetrahedral
Square Planer

21. Coordination polyhedron:
The spatial arrangement of the ligand atoms which are directly attached to the
central atom/ion defines a coordination polyhedron about the central atom.
e.g., For example, [Co(NH3)6]3+ is octahedral, [Ni(CO)4] is tetrahedral and
[PtCl4]2– is square planar.
Co-ordination Compound

22. Classification of Complex
i. Based on the type of Ligand
Homoleptic Complex Heteroleptic
Complex
The complex in which
central metal is
surrounded by one type of
ligand.
The complex in which central
metal is surrounded by more
than one type of ligand.
[Co(NH3)6]+1 [Co(NH3)4Cl2]+1

23. Classification of Complex
ii. Based on charge on co-ordination sphere
Cationic sphere
Complex
Anionic Sphere Complex
The complex which
having positive charge
on coordination sphere.
The complex which
having negative charge
on coordination sphere.
[Co(NH3)6]+1 [Fe(CN)6]-4
Neutral Sphere Complex
The complex which
having zero charge on
coordination sphere.
[Ni(CO)4]

24. IUPAC nomenclature of coordination compound
1. [MLn]
Ligand name-central metal name-(oxidation number)
2. X[MLn] X= cation
Cation name- Ligand name-central metal name +ate -(oxidation
number)
3. [MLn]Y Y= anion
Ligand name-central metal name-(oxidation number)-anion name
4. [MLn]n-
Ligand name-central metal name-(oxidation number)+ate-ion
5. [MLn]n+
Ligand name-central metal name-(oxidation number)-ion

25. Cl-  Chloro
Br-  Bromo
F-  Floro
I-  Iodo
CN- 
Cyano
SO4
-  Sulphato
NO3
-  Nitrato
CO3
-2 
Carbonato
OH-  Hydroxo
C2O4
-2  Oxalato
NO2
-  Nitro
ONO-  Nitrito
SCN-  Thyiocynato
NCS- 
NH3  Amine
CO  Carbonyl
H2O  Aqua
en  Ethylene di
amine

26. Normal Metal
Name
Symbol Normal Metal
Name+ate
Al Aluminium Aluminat
e
Co Cobalt Cobaltate
A
u
Gold Aurate
Mn Manganese Mangante
Pt Platinu
m
Platinat
e
Cr Chromium Chromate
C
u
Copper Cuprate
Fe Iron Ferrate
Ni Nickel Nickela
te
Zn Zinc Zincate

27. [Cr(NH3)3(H2O)3]Cl3
First Step Ligand name
Triaminetriaqua
Second Step Metal name
Triaminetriaquachromium
Third Step Oxidation number
Triaminetriaquachromium(III)
Fourth Step Anion name
Triaminetriaquachromium(III) chloride

28. Tetraamminediaquacobalt(IlI)
chloride
Potassium tetracyanidonickelate(II)
Tris(ethanp-1,2-diamine) chromium(III) chloride
Amminebromidochloridonitrito-N- platinatc(II)
Dichloridobis(ethane-l ,2-diamine) platinum (IV)
nitrate
Iron(III)hexacyanidoferrate(II)
Write the formulas for the following coordination
compounds:
[CO(NH3)4(H2O)2]Cl3
K2[Ni(CN)4]
[Cr(en)3]Cl3
[Pt (NH3) Br Cl (N02)]–
[PtCl2(en)2](N03)2
Fe4[Fe(CN)6]3
(a) [CO(NH3)6]Cl3
(b) [CO(NH3)Cl]Cl2
(C) K3[Fe(CN)6]
(d) [K3[Fe(C2O4)3]
(e) K2[PdCl4]
(f) [Pt(NH3)2ClNH2CH3]Cl
(a) hexaamminecobalt (III) chloride
(b) pentaamminechloridocobalt (III) chloride
(c) potassium hexacyanoferrate (III)
(d) potassium trioxalatoferrate (III)
(e) potassium tetrachloridoplatinum (II)
(f) diamminechlorido (methylamine) platinum(II) chloride.

29. Chelation
Chelation is a process in which a polydentate ligand bonds to a metal ion,
forming a ring. The complex produced by this process is called a chelate, and the
polydentate ligand is referred to as a chelating agent.
Ethylenediaminetetraaceticacid acid (EDTA) is a hexadentate
ligand and can bind a Metal via multiple "teeth" (left) Unbound
EDTA ion and (right) EDTA bound to a generic transition metal.
The Chelate Effect
The chelate effect is the enhanced affinity of
chelating ligands for a metal ion compared to the
affinity of a collection of similar nonchelating
(monodentate) ligands for the same metal.

30. Isomerism in Coordination Compounds
Isomer:
 Two or more compounds having same molecular formula, but different physical
properties and chemical properties are called Isomers.
 Isomers are two types.
Stereoisomer
Two or more isomers having same
linkage among the constituent atoms but
different arrangement of atoms in space.
Structural Isomer
Two or more isomers having different
linkage among the constituent atoms but
same arrangement of atoms in space.
Geometrical
isomer/
Disteromer
Optical
isomer/
Enantiomer
Linkage
isomer
Coordinatio
n isomer
Ionization
isomer
Solvate
isomer/
Hydrate
isomer
Cis-Isomer Trans-
Isomer
Dextrorot
atory/d-
form/(+)
Levorotator
y/l-form/(-)

31. Isomerism in Coordination Compounds
Stereoisomer:
Geometrical/ Di stereomer
The non super imposable mirror
image isomer are called as
Geometrical Isomer.
Optical Isomer/
Enantiomers
The non super imposable mirror
image isomer. Which are *chiral
are called as Optical Isomer.
*Chiral
The central metal atom which attached to different-different atom are called Chiral.
Cis-Isomer Trans-
Isomer
Dextrorotatory/d-
form/(+)
Levorotatory/l-form/(-)
The isomer in
which identical
groups occupy the
adjacent position
The isomer in
which identical
groups occupy the
opposite position
The optical isomer
which rotate the
plane polarized
light towards right
or clockwise.
The optical isomer
which rotate the
plane polarized
light towards left
or anti-clockwise.

32. Geometric Isomerism
Optical Isomerism

33.  This type of isomerism arises in Heteroleptic complexes due to different
possible geometric arrangements of the ligands.
 Important examples of this behavior are found with coordination numbers
4 and 6.
 In a square planar complex of formula [MX2L2] (X and L are unidentate),
the two ligands X may be arranged adjacent to each other in a cis isomer,
or opposite to each other in a trans isomer.
 Other square planar complex of the type MABXL (where A, B, X, L are
unidentates) shows three isomers-two cis and one trans.
 Such isomerism is not possible for a tetrahedral geometry, but similar
behavior is possible in octahedral complexes of formula [MX2L4] in which
the two ligands X may be oriented cis or trans to each other
Geometrical Isomerism application

34.  This type of isomerism also arises when
di-dentate ligands L – L [e.g., NH2 CH2
CH2 NH2 (en)] are present in complexes
of formula [MX2(L– L)2]
Geometrical Isomerism application
Geometrical isomers (cis and trans) of [CoCl2(en)2]
 Another type of geometrical isomerism
occurs in octahedral coordination entities
of the type [Ma3b3] like
[Co(NH3)3(NO2)3].
 If three donor atoms of the same ligands
occupy adjacent positions at the corners of
an octahedral face, we have the facial (fac)
isomer. When the positions are around
the meridian of the octahedron, we get the
meridional (mer) isomer

35. Planar Isomers

36. Octahedral Isomers

37. Linkage
Isomerism
Linkage isomerism arises in a coordination compound
containing ambidentate ligand. e.g., M–NCSM-SCN
[Co(NH3)5(NO2)]Cl2  -ONO gives Red colour, -NO2 gives
Yellow colour
Coordination
Isomerism
This type of isomerism arises from the interchange of ligands
between cationic and anionic entities of different metal ions
present in a complex. e.g.,
[Co(NH3)6][Cr(CN)6][Cr(NH3)6][Co(CN)6]
Ionisation
Isomerism
This form of isomerism arises when the counter ion in a complex
salt
is itself a potential ligand and can displace a ligand which can
then
become the counter ion.
e.g., [Co(NH3)5(SO4)]Br  [Co(NH3)5Br]SO4
Solvate
Isomerism
This form of isomerism is known as ‘hydrate isomerism’ in case
where water is involved as a solvent.
Solvate isomers differ by whether or not a solvent molecule is
directly bonded to the metal ion or merely present as free
solvent molecules in the crystal lattice.
[Cr(H2O)6]Cl3 (violet)  solvate isomer
[Cr(H2O)5Cl]Cl2.H2O (grey-green).

38. Valence Bond Theory
Coordination number 6 Coordination no 4
Ligand Strong Weak Strong Weak
Pairing Pairing No pairing Pairing No pairing
Hybridization d2sp3 Sp3d2 dsp2 sp3
Geometry Octahedral Octahedral Square planner Tetrahedral
Spin Low High Low High
Calculate the O.N. of metal
Check C.N. of metal
Valence shell e-configuration Metal atom
Valence shell e- configuration of Metal ion
Follow the table

39. Valence Bond Theory
Strong Ligand CN-, CO, NH3 with M+3 oxidation state,
all polydentate ligand
Weak Ligand  Cl-, F-, Br-, I-, OH-, NH3 with M+2
oxidation state
Magnetic Behavior
Diamagnetic  Pairing of electron
Paramagnetic  Non pairing of electron

40. Limitation of Valence Bond Theory
1.It involves a number of assumptions.
2.It does not give quantitative interpretation of magnetic
data.
3.It does not explain the colour exhibited by coordination
compounds.
4.It does not give a quantitative interpretation of the
thermodynamic or kinetic stabilities of coordination
compounds.
5.It does not make exact predictions regarding the
tetrahedral and square planar structures of 4-coordinate
complexes.
6.It does not distinguish between weak and strong ligands.

41. Crystal Field Theory
dxy dyz dzx dx2-y2 dz2
dx2-y2 dz2
dxy dyz dzx
Isolate state Metal-Ligand bond state
eg  doubly degenrate
t2g  Triply degenrate
10 dq= 1∆ꓸ
Crystal Field parameter
3
5
∆ꓸ=0.6∆ꓸ
2
5
∆ꓸ=0.4∆ꓸ
Crystal field splitting in Octahedral coordination
Compound

42. Crystal Field Theory
For Octahedral Complex
(C.N.=6)
Ligand (L)
Strong Field Ligand (SFL) Weak Field Ligand (WFL)
Donor atom = C, N, P Donor atom = O, S, X=(Cl, F, Br, I)
CO, CN, NC, (en), EDTA,
NH3
SNC, SCN, S-2, F, Cl, Br, I, H2O,
OH-
Spectrochemical series
I– < Br– < SCN– < Cl– < S2– < F – < OH– < (C2O4 )2– < H2O
< NCS–< edta4– < NH3 < en < CN– < CO

43. Crystal Field Theory
dxy dyz dzx dx2-y2 dz2
dx2-y2 dz2
dxy dyz dzx
Isolate state Metal-Ligand bond state
e
t2
10 dq= 1∆ꓸ
Crystal Field parameter
3
5
∆ꓸ=0.6∆ꓸ
2
5
∆ꓸ=0.4∆ꓸ
Crystal field splitting in Tetrahedral coordination
Compound
Splitting of d-orbitals in tetrahedral crystal
Average energy of the d-orbitals in
spherical crystal field

44. Colour in coordination compounds
[Ti(H2O)6]3+
Oxidation state of Ti =
+3
Valence shell e- configuration of Ti = 3d1 4s0
Ground State Excited State
eg
tg
eg
tg
ℎ𝜈
[Ti(H2O)6]3+ violet in
colour
Blue green light is absorbed
Voilet light is excreted
d-d transition

45. Limitation of Crystal Field Theory
1. The assumption that the interaction between metal-ligand is purely
electrostatic cannot be said to be very realistic.
2. This theory takes only d-orbitals of a central atom into account. The s
and p orbits are not considered for the study.
3. The theory fails to explain the behaviour of certain metals which cause
large splitting while others show small splitting. For example, the theory
has no explanation as to why H2O is a stronger ligand as compared to
OH–.
4. The theory rules out the possibility of having p bonding. This is a serious
drawback because is found in many complexes.
5. The theory gives no significance to the orbits of the ligands. Therefore, it
cannot explain any properties related to ligand orbitals and their
interaction with metal orbitals

46. Bonding in metal carbonyl
The metal-carbon bond in metal carbonyls possess both sigma and pi character.
The M–C s bond is formed by the donation of lone pair of electrons on the carbonyl
carbon into a vacant orbital of the metal.
The M–C p bond is formed by the donation of a pair of electrons from a filled d orbital of metal into the
vacant antibonding p* orbital of carbon monoxide.

47. Importance & application of coordination
compounds
1. Metallurgical processes
• Metals can be purified by the formation and subsequent
decomposition of their coordination compounds. For example,
impure nickel is converted to [Ni(CO)4], which is decomposed to
yield pure nickel.
• Solutions of the complexes like [Ag(CN)2]– and [Au(CN)2]– can
be used for the smooth and even electroplating of metals by gold
or silver.
2. Analytical chemistry
• In analytical chemistry [Ni(DMG)2]2+ complex is used in the
detection of Ni in chocolates.
• EDTA is used in the estimation of Ca2+ and Mg2+ in hardwater.
The Ca2+ and Mg2+ ions form stable complexes with EDTA.
• Coordination compounds are used as catalysts for many industrial

48. Importance & application of coordination
compounds
3. Medicinal chemistry
• In medicine, cisplatin, a cis isomer of [Pt(Cl)2(NH3)2] is used in
the treatment of cancer.
• Chlorophyll, a pigment responsible for photosynthesis, is a
coordination compound of magnesium.
• Also, haemoglobin, the red pigment of blood which acts as oxygen
carrier is a coordination compound of iron.
4. Other uses
• In black and white photography, the developed film is fixed by
washing with hypo solution which dissolves the undecomposed
AgBr to form a complex ion, [Ag(S2O3)2]3–..