PAWAN WAGH ACADEMY
MAKING MATHEMATICS SIMPLE & INTERESTING
Class 12th
Notes
Topic- Co-ordination compounds
Co-ordination compound-
The compound which consists of central metal atom
or ion surrounded by atoms or molecules is called as
co-ordination compound.
Co-ordination compound=metal + Ligand
Central metal ion-
The centrally situated electron pair acceptor or lewis
acid are called as metal ion.
Ligand-
The electron pair donors or lewis bases are called as
Ligands.
o e- pair acceptor – Lewis acid – metal
o e-pair donor – Lewis Base – Ligand
o [M (L)n) – Co-ordination compound
Lewis lewis
Acid base
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Co-ordinate bond-
L M
Ligand Metal
(अमीर) (भिखारी)
Types of Ligands
(on the basis of density
or electron donor atom)
Polydenate ligand Ambidenate
Monodenate ligand
A ligand, which has two
Ligand A ligand which has two
or more donor atom,
A ligand, which has attached central metal donor atom, and at one
single donor atom, atom, is called as time, uses single atom
attached to central polydenate ligand. for donation is called
metal atom, is called ligand.
as monodentate
ligand.
ex.
ex.
Bidentate ligand Tridentate ligand
Hexadentate ligand
(Bi=2) (tri=3) (Hexa=6)
EDTA
(CH2)2
H2N
Ethylene diammine
NH2
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Diethylenetriamine
Co-ordination sphere-
The central metal atom and ligands attached to it are
enclosed in a square bracket, which is called as
co-ordination sphere.
ex [M(L)n]- co-ordination sphere
Counter ions-
The ionisable groups, present outside the bracket
are called as ions.
Ex. K4[Fe(CN)6]
Counter ions
Charge Number-
The net charge residing on the complex ion, is called
as charge number.
Oxidation number or oxidation state-
The charge carried by the metal ion is called as
oxidation state or number.
Co-ordination number of metal ion-
The number of liquid donor atoms directly attached
to the metal atom is called as Co-ordination number
ion.
ex. [M(L)2] co-ordination No’s = 2
[M(L)6] co-ordination No’s = 6, where
L= monodentate ligand
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Double salt Co-ordination complex
A salt which dissociates A complex which
into simplex ions dissociation with one
completely in water is complex ion in water, is
called as Double salt. called as co-ordination
ex. complex
Fe(SO)4(NH4) SO4 6H2O
is mohr’s salt Ex.
K4[Fe(CN)6] 4k+[Fe(CN) 6] 4-
Fe(SO4) (NH4)2SO4 6H2O
Fe+2 + 2NH4(+) + 2SO42-
Werner’s theory of co-ordination complex-
a. The metal in a complex shows two types of
valencies- Primary valency
Secondary valency
b. Primary valency is ionisable and are satisfied by
anions.
c. Secondary valency is non-ionisable and are
satisfied by anions or neutral ligands.
d.Secondary valency shows fixed arrangement,
around central metal, which is called as geometry
of complex.
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In a complex.
Relation of Co-ordination number and geometry of
complex.
Tetrahedral
CN=4-Geometry
Square planner
CN=6-Geometry – Octahedral
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Classification of complex
On the basis of types of On the basis of charge on
ligands complex or co-ordination
sphere
Homoleptic complex Hetroleptic complex
The complex in which, The complex in which
metal is attached to metal is attached to
only 1 type of ligand, is more than 1 type of
called as Homoleptic ligand is called as
complex Hetroleptic complex
ex. [CO(NH3)6]+3 ex. [Co(NH3)6)Cl2]1(+)
Anionic sphere Neutral sphere
Cationic sphere complex
complex
complex
The complex which have The complex which have
The complex which have negatively charged co- neither positive nor negative
positively charged co- ordination sphere is called charge are called as neutral
ordination sphere is called as Anionic sphere complex sphere
as cationic sphere complex
ex. [Ni(CN)4]2- ex. [Ni(CO)4]
ex [Zn(NH3)4] +4
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IUPAC Nomenclature of co-ordination compound
a. [M(L)n]
Ligand name – metal name – (oxidation no’s)
b. [M(L)n]X (X=counter anion)
Ligand name – metal name – (oxidation No’s) –
counter anion name
c. Y[M(L)n] (Y = counter cation)
Counter cation name – ligand name – metal name –
(oxidation no’s)
d.[M(L)n]b+ (b=charge)
Ligand name- metal name – (oxidation no’s) + ion
e. [M(L)n]b- (b=charge)
Ligand name + o – metal name + ate- (oxidation
no’s) + ion
o Never write di,tri,tetra, in front of name of counter
cation or counter anion.
o Always write di, tri, tetra in front of name of ligand
directly attached to metal, in the co-ordinate sphere.
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EAN- (always asked in exam)
EAN = effective atomic number
EAN= atomic number + 2 x number - oxidation state
of metal of ligands state of metal
(central atom) attached to
metals
Ex [Fe(CN)6]4- = z = atomic number = Fe = 26
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Firstly calculate oxidation state of metal-
[Fe(CN)6]4- no of ligand = 6
X+6 (-1) = -4
x-6 = -4
x=-4+6
x= +2 - oxidation state of metal
EAN = 26 + (2x6) – 2
= 26+12-2
= 26+10
EAN = 36
Isomers
The different compounds that have the same
molecular formula are called as Isomers.
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Isomers in co-ordination compound
Isomers
Stereoisomers Constitutional isomers or structural
The isomers that have same linkage isomers
among the constituent atom, but The isomers that have different linkages
different arrangement are called as among the constituent atom, but
stereoisomer chemical formulae is same is called as
structural isomers
Geometric isomers or Optical Isomer or
diastereomers Enantiomers
The isomers that are non- The isomers that are non-
superimposable mirror images superimposable chiral are
of each other are called as called as Enantiomers
Geometric isomers.
Cis isomer
Trans isomer
Identical ligand
occupy adjacent Identical ligand occupy
position opposite position
In square In octahedral
In square In planner complex
planner octahedral complex
complex
Dextrorotatory (d) Levorotatory (l)
Which rotates plane Which rotates plane
polarized light to the polarized light to the
right. left.
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Constitutional isomers or structural isomers
Ionization isomers
Linkage isomer Co-ordination isomers.
The isomer in which,
The isomer in which The isomer in which there
there is exchange of
ligand have two is a exchange of ligands
ligands between co-
different donor atoms, between co-ordination
oxidation and ionization and ionization sphere is
and co-ordinates to
sphere is called as
metal with different co-ordination isomers
ionization isomers
donor atoms is called as
ex. [Co(NH3)6] [Cr(CN)6] &
linkage isomers ex. [Co(NH3)5So4] Br and [Cr(NH3)6] [Co(CN)6]
[Co(NH3)5 Br] So4
ex. [Co(NH3)5 (NO2)]+2&
[Co(NH3)5 (ONO)]+2
Solvate or Hydrate isomers
The isomer which sows involve ment of water
molecule (H2O) as a ligand and free molecule is
called as solvate or hydrate isomer
Ex.[Cr(H2)6]Cl3 and [Cr(H2O)5cl] Cl2.H2O
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Cis and trans isomer in square planner complex
(CN =4)
1.
2.
Cis and trans isomer in octahedral complex (CN=6)
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Optical isomers (enantiomers) in octahedral complex
1.
2.
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Stability of co-ordination compounds depends on
the value of Stability constant.
o Higher is the value of the Stability constant (K),
higher is the stability of complex.
Stability of complex depends on two factors
Charge size ration of metal Nature of ligand
ion More stronger is the ligand,
Higher is charge to size more stable is the complex
ratio of metal ion, higher is formed
the stability of complex
Poslutates of valence bond theory or (VBT) or
Hybridization
a. Metal ion provides vacant d-orbitals for formation of co-ordinates
bond.
b. Vacant d, s and p-orbitals of metals take part in hybridization.
c. Number of vacant hybrid orbital=Number of ligand
donor atom.
d. Vacant orbital of metal overlap with filled orbital of ligand.
e. If ligand are stronger or powerful, then pairing occurs, and inner
orbital complexes are formed.
f. If ligand are weaker, than pairing do not occurs, and outer
complexes are formed.
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Crystal field theory-
The crystal field theory has been widely accepted.
The assumptions of the crystal field theory are as
given below-
a. The ligands are treated as point charges
The interaction between metal ion and ligand is
purely electrostatic in nature
b. In an isolated gaseous atom
dxy, dyz, dzx, dz2, dx2-y2- have same energy
c. When ligand approaches the metal ion, they crate
crystal field around the metal ion.
d.The field created by the ligand around the metal
is, not symmetrical, as a result of which, d-orbitals
split as-
dx2-y2, dz2 eg
d
dxy, dyz, dzx – t2g
e. The two sets of d-orbitals include t2g and eg. The
separation of engineers of these two sets of
orbitals t2g and eg is called as crystal field
splitting parameter
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f. Crystal field splitting parameter(∆)
∆o ∆t
For octahedral for tetrahedral
Complex complex
g. ∆o𝛼 strength of ligands
Strong field ligand Weak field ligand
Involves donor atom(C,N,P) Involves donor (X,O,S)
Ex.CN-,NC-,CO,NH3,EDTA, en s=atom
(ethylene diamine) Ex halogen (F-, Cl-, Br-, I-),
SCN-, C2O42-
Crystal field splitting in octrahedral complex.
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Crystal field splitting in tetrahedral complex.
(t2g)
dxy dyz dzx +0.4∆o
dxy dyz dzx d2x-y2 dz2
∆o
-0.6∆o
or
(eg) logd
d x-y2 dz2
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