Transcript Chapter 1: Matter and Measurement

Coordination Chemistry
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Coordination Chemistry
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Werner/Jorgensen Controversy
Sophus Jorgensen
Alfred Werner
“Probably the greatest conceptual contribution to inorganic
chemistry—comparable in both direct and indirect impact to the
concept of the tetrahedral carbon atom in organic chemistry—is
Alfred Werner’s concept of coordination compounds and his
general theory of how they behave.” Albert Cotton
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Chelation
 Metals are able to bind or chelate (greek to claw) to other
molecules or ions in solution called ligands
 Common Ligands are Lewis bases (electron pair donors)
◦ Monodentate
H
N
H
H
Bidentate
H
N CH2CH2 N
H
H
H
 Common Metal ions are Lewis acids (electron pair acceptors)
 Coordinate Covalent bonds are formed L → M
 Complexes using polydentate ligands are called chelates
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Table 24.3 Some Common Polydentate
Ligands (Chelating Agents)
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24-1Werner’s Theory of Coordination
Compounds: An Overview
 Compounds that contain metal complexes are
called coordination compounds.
 CoCl3 and NH3.
 [Co(NH3)6]Cl3 and [CoCl (NH3)5]Cl2
 Differing reactivity with AgNO3.
Alfred Werner
1866-1919
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Werner’s Experiment
 As a 26 year old lecturer Werner did the following experiment
Empirical formula
#
Cl- ions Complex
ions Ag+ ppt
Co(Cl)3(NH3)6
Orange/yellow
4
3
[Co(NH3)6]3+
+ 3 Cl-
Co(Cl)3(NH3)5
purple
3
2
[Co(NH3)5Cl]2+
+ 2 Cl-
Co(Cl)3(NH3)4
Green/violet
2
1
[Co(NH3)4Cl2]1+
+ 1 Cl-
 Wener proposed that metals exhibit both primary and
secondary valences
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Werner’s Theory
 Two types of valence or bonding capacity.
 Primary valence (oxidation number).
◦ Based on the number of e- an atom loses in forming the ion.
 Secondary valence (coordination number).
◦ Responsible for the bonding of other groups, called
ligands, to the central metal atom.
[Co(NH3)6]Cl3 → [Co(NH3)6]3+ + 3 Cl[CoCl(NH3)5]Cl2 → [CoCl(NH3)5]2+ + 2 ClSlide 8 of 59
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Coordination Number
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Ethylene Diamine
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EXAMPLE 24-1
Relating the Formula of a Complex to the Coordination
Number and Oxidation State of the Central Metal. What
are the coordination number and oxidation state of Co in the
complex ion [CoCl(NO2)(NH3)4]+?
Solution:
The complex has as ligands
1Cl, 1NO2, 4NH3 .
The coordination number is 6.
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EXAMPLE 24-1
Charge on the metal ion:
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Isomerism
Werner predicted there would be only two isomers of
[CoCl2(NH3)4]+ and mailed them to Jorgensen. He received
the Nobel prize in 1913.
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Isomerism
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Examples of Structural Isomerism
Ionization Isomerism
[CrSO4(NH3)5]Cl
[CrCl(NH3)5]SO4
pentaaminsulfatochromium(III) chloride
pentaaminchlorochromium(III) sulfate
Coordination Isomerism
[Co(NH3)6][CrCN6]
[Cr(NH3)6][CoCN6]
hexaaminecobalt(III) hexacyanochromate(III)
hexaaminechromium(III) hexacyanocobaltate(III)
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Linkage Isomerism
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Stereoisomerism: Geometric Isomerism
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Geometric Isomerism
How many
isomers would
[CoCl3(NH3)3]
have?
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Geometric Isomerism
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Optical Isomerism
Chiral shapes are not super imposable on their mirror image
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Chirality or Handedness
Triethylenediamine cobalt(III) is a chiral molecule it differs
only in how it interacts with another chiral object. “You can
not put a right handed glove on a left hand”. Left and right
circularly polarized light is an example of a chiral object.
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Optical Isomerism
enantiomers
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Optical Activity
We are made up of chiral molecules –
l-amino acids, protein alpha helix, the
DNA duplex, and sugars.
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dextrorotatory dlevorotatory l-
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24-3 Nomenclature
 In names and formulas of coordination compounds,
cations come first, followed by anions.
 Anions as ligands are named by using the ending –o.
 Normally:
◦ – ide endings change to –o.
◦ – ite endings change to –ito.
◦ – ate endings change to –ato.
 Neutral molecules as ligands generally carried the
unmodified name.
 If the complex is an anion the ending –ate is attached
to the name of the metal.
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Table 24.2 Some Common Monodentate
Ligands.
– ide endings change to –o
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– ate endings change to –ato
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24-5 Bonding in Complex Ions:
Crystal Field Theory
 Consider bonding in a complex to be an
electrostatic attraction between a positively
charged nucleus and the electrons of the ligands.
 Electrons on metal atom repel electrons on ligands.
 Focus particularly on the d-electrons on the metal ion.
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Octahedral Complex and d-Orbital Energies
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Electron Configuration in d-Orbitals
Δ
P
Hund’s Rule
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Pairing Energy Considerations
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Spectrochemical Series
Large Δ
Strong field ligands
CN- > NO2- > en > py  NH3 > EDTA4- > SCN- > H2O >
ONO- > ox2- > OH- > F- > SCN- > Cl- > Br- > I-
Small Δ
Weak field ligands
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Electron Configuration in d-Orbitals
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Effect of Ligands on the Colors of
Coordination Compounds
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Absorption Spectrum
max
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Light Absorption and Transmission
[Ni(H2O)6}2+
Ni(NH3)6]2+
[Ni(en)3]2+
Transmitted
Green
Blue
Purple
Absorbed
(red)
Do hc/
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(orange)
(yellow)
700 nm
600 nm
570 nm
small
medium
large
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Werner’s Theory of Coordination
Compounds
 CoCl3 and NH3.
 [Co(NH3)6]Cl3 and [CoCl (NH3)5]Cl2
Alfred Werner
1866-1919
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Presented by: Sudhir Kumar Maingi PGT CHEMISTRY
K.V. No. 1 PATHANKOT, JAMMU REGION
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