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Isomers of Coordination Complexes Coordination Chemistry. Geometry. Coordinate Number (CN): Number of donor atoms bonded to metal 2- Coordinate - linear 4 - Coordinate tetrahedral and sq planar ML 4 , Pt(II) is always CN = 4 6- Octahedral ML 6 , Cr(III) and Co(III) CN = 6 - PowerPoint PPT Presentation
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12.2.00 12:06 AM1 24.2 Isomers of Coordination Complexes
Isomers of Coordination Complexes
Coordination Chemistry
12.2.00 12:06 AM2 24.2 Isomers of Coordination Complexes
GeometryCoordinate Number (CN):
Number of donor atoms bonded to metal2- Coordinate - linear4 - Coordinate tetrahedral and sq planar
ML4 , Pt(II) is always CN = 4
6- OctahedralML6, Cr(III) and Co(III) CN = 6
CN influence by size of metal ion
surrounding ligand
Small metal /large ligand - Low coordinate number
Large metal / small ligand - High coordination number
i.e., FeF63- and FeCl4
- only
12.2.00 12:06 AM3 24.2 Isomers of Coordination Complexes
Historic PerspectiveDuring early / mid 1800’s bonding was not well understood. Most widely accepted theory on bonding was the chain theory supported by Sophus Jorgensen (1837 - 1914). The structure of Co(NH3)6Cl3 was explained in the classrooms using this theory in the late 1800’s. In 1890 Alfred Werner proposed a new bonding scheme and wrote a paper called “coordination theory”. In 1913 Werner won the 14th Noble Prize for his work.
12.2.00 12:06 AM4 24.2 Isomers of Coordination Complexes
Isomers -Same formula different properties. i.e., N2O NNO
or NONStructural isomer
Compd with different atomic bond connectivity. Coordination sphere isomer Linkage isomer
Stereoisomer Same atomic connectivity but different arrangement.Geometrical isomer Optical isomer
12.2.00 12:06 AM5 24.2 Isomers of Coordination Complexes
Structural isomer-Different Atomic connectivityCoordinate sphere isomer - Complexes in which
the ligand is bonded differently to the metal.Co 3Cl 6H2O
H
HH
Cl
OO
H
Co
H
O
OH
Cl
H
H Cl • 2H2O
H
H
H
OO
O
H
H
H
Co
O
H
HO
H
O
H
H
H
Cl3 H
H
H
O
H
O
O
H
H
Co
H
O
Cl
H
O
H
H
Cl2•H2O
i) six H2O in coordination sphere.
Violet
ii) five H2O and one Cl in coordination sphere.
Dark Green
iii) four H2O and two Cl in coordination sphere.
Green
12.2.00 12:06 AM6 24.2 Isomers of Coordination Complexes
Linkage IsomersLinkage isomer - Isomer complexes in
which the ligand coordinates to the metal by different donor atoms. i.e., Nitrite ion, NO2
-
Other ligand capable of switching donor atomSCN-, CN-, 2.2’-bipyridine
Nitrito ligand as an O-donorNitro ligand as an N-donor
12.2.00 12:06 AM7 24.2 Isomers of Coordination Complexes
Linkage Isomer of 2,2’-bipyridine
Two compounds formed by the linkage isomer of bpy is shown. Small changes in ligand bonding could result in dramatic chemical property change.
C
C
C
C
C
C
C
C
C
N
C
C
C
C
N
N
C
C
Ir
C
C
C
NC
N
C
N
C
C
C
C
C
C
C
C
C
CC
C
C
C
C
C
C
C
C
C
N
C
C
C
N
N
C
C
Ir
C
C
C
NC
N
C
N
C
C
C
C
C
C
C
C
C
C
Nitrogen bonded
Carbon Bonded
12.2.00 12:06 AM8 24.2 Isomers of Coordination Complexes
Geometric Stereoisomer
Geometric isomer - Compounds with similar atomic connectivity but different atomic arrangement in space.
Diaminedichloroplatinum(II)
Cisplatin transplatinDiaminecisdichloroplatinum(II)
diaminetransdichloroplatinum(II)
12.2.00 12:06 AM9 24.2 Isomers of Coordination Complexes
Mirror ImageMirror images cannot be exactly superimposed over
each other. Complexes which form mirror images are called chiral
Most of the human body is chiral (the hands). Enzymes are the most highly chiral substances known.
12.2.00 12:06 AM10 24.2 Isomers of Coordination Complexes
Optical Isomers
Optical isomer - Isomer complex in which the atomic connection are the same but arrangement is such that the two complexes are not superimposable.
Optical isomers are called enantiomer.
Chiral Complexes are also called enatiomers
12.2.00 12:06 AM11 24.2 Isomers of Coordination Complexes
Optical Inorganic Isomers
Enantiomer - Isomer that are mirror image to each other.
Handedness:
“R” “S”
Molecules/Ions that have enantiomer are chiral
12.2.00 12:06 AM12 24.2 Isomers of Coordination Complexes
Optical Isomer and Interaction with Light
Enatiomers rotate the plane of polarized light.
Dextrorotatory- “d” isomer Complex which rotates plane of polarized light to
the right.Levorotatory- “l” isomer
Complex which rotates plane of polarized light to the left.
Chiral molecules are optically active because effect on light.
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