Download Chemistry of Coordination Compounds Chapter 24 Nov. 2006

Chemistry of Coordination
Compounds
Chapter 24
Nov. 2006
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s1
The Position of the Transition Elements on
‹
the Periodic Table
d
s
s2
d3
Œ
s
d
d4 d5
s2p1·············s2p6
d10s1
d10 ‚ d10s2
Ca
Sr
Ba
Ra
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Electron Configurations and other properties of the
first row transition Metals
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Oxidation States of the 1st Row Transition Metals
(most stable oxidation numbers are shown in red)
3d3
3d4
3d5
3d6
3d7
3d8
3d9
3 d10
Ca
3d104s1
Zn
uOs
+8
+4
d0
+2
+2
v -1
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Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
22.2
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Coordination Compounds
⎧
⎧
⎧cation
⎪
⎪Metal ⎨
⎩atom
⎪a complex ion ⎪
⎪
⎨
A coordinate compound ⎨
⎪ligants ⎧molecules
⎨
⎪
⎪
⎩ions
⎩
⎪
⎪⎩a counter ion
[Cr(H2O)4Cl2] Cl
[Co(NH3)4Cl2] SO4
K4 [Fe(NCS)6]
The molecules or ions that surround the metal in a complex ion
are called ligands.
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Coordination Compounds
H
H
H H H
••
Cl
••
-
C
••
••
N
••
••
•O• •
••
A ligand has at least one unshared pair of valence electrons
O
The atom in a ligand that is bound directly to the metal
atom is the donor atom.
atom
Ligands with:
one donor atom
monodentate
two donor atoms
bidentate
three or more donor atoms polydentate
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H2O, NH3, Clethylenediamine
EDTA
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Coordination Compounds
bidentate ligand
••
H2N
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CH2
CH2
••
NH2
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Coordination Compounds
polydentate ligand
(EDTA)
HOOC
CH2
H2C
COOH
N CH2 CH2 N
HOOC
CH2
H2C
COOH
Bidentate and polydentate ligands
are called chelating agents
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Naming Coordination Compounds
• The cation is named before the anion.
• Within a complex ion, the ligands are named
first in alphabetical order and the metal atom
(or ion) is named last.
• The names of anionic ligands end with the
letter o. Neutral ligands are usually called by
the name of the molecule.(The exceptions are
H2O (aquo), CO (carbonyl), and NH3
(ammine)).
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Naming Coordination Compounds
• When several ligands of a particular kind are
present, the Greek prefixes di-, tri-, tetra-, penta-,
and hexa- are used to indicate the number. If the
ligand contains a Greek prefix, use the prefixes
bis, tris, and tetrakis to indicate the number.
• The oxidation number of the metal is written in
Roman numerals following the name of the
metal.
• If the complex is an anion, its name ends in –ate.
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Naming Coordination Compounds
K
[Fe(CN)
]
4
6
N cation
anion
[Co(NH
)
]Cl
3
6
N3
cation
anion
4-
[Fe(NH
)
]
3
6
anion
Potassium
hexacyanoferrate(II)
cation
anion
Hexaamminecobalt(III)
chloride
anion
cation
hexa
ferrate
(II)
ion
N cyano
N Fe anion N
6
CN -
oxidation
number
tris
(ethylenediamine)
cobalt
(III)
chloride
[Co(en)
]Cl
N
3
3
N
N 6
Co
cation
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anion
ligand name
oxidation
number
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Naming Coordination Compounds
English Name
Copper
Gold
Iron
Lead
Silver
Tin
Anion Name
Cuprate
Aurate
Ferrate
Plumbate
Argentate
Stannate
Write the structural formula corresponding to each of the
following IUPAC names:
a. hexaaquairon(II) chloride;
b. tetraamminedichloroplatinum chloride
c. Potassium hexachloroplatinate(IV)
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Structure of Coordination Compounds
Fe
→ [Fe(CN)6 ]
N + CN
N ⎯⎯
2+
lewis acid
-
4-
lewis base
Three important properties of complexes:
a. Isomerism
b. Color
c. Paramegnetism
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Isomerism of Coordination Compounds
⎧Constitutional isomerism
Isomerism ⎨
⎩Steroisomerism
Constitutional isomerism: are isomers that differ in
how the atoms are joined together.
Stereoisomerism: are isomers in which the atoms are
bonded to each other in the same order, but differ in
the precise arrangement of the atoms in the space.
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Isomerism of Coordination Compounds
Constitutional isomerism:
[Co(NH 3 )5SO 4 ]Br and [Co(NH 3 )5 Br]SO 4
[Cu(NH 3 ) 4 ][PtCl4 ] and [Pt(NH 3 ) 4 ][CuCl4 ]
[Co(NH 3 ) 4 ( O
N O 2 )]Cl2
N NO)]Cl2 and [Co(NH 3 ) 4 ( N
doner
atom
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doner
atom
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Constitutional isomerism:
[Co(NH 3 )5 ( N
N O 2 )]Cl2
doner
atom
[Co(NH 3 )5 ( O
N NO)]Cl2
doner
atom
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Isomerism of Coordination Compounds
⎧Constitutional isomerism
⎪
Isomerism ⎨
⎧Geometric isomerism
⎪Steroisomerism ⎨Optical isomerism
⎩
⎩
Geometric isomers: are isomers in which the atoms are
bonded to each other in the same way, but differ because some
atoms occupy different relative position in space.
cis-[Pt(NH3)2Cl2]
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trans-[Pt(NH3)2Cl2]
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Isomerism of Coordination Compounds
trans
cis
cis-[Co(NH3)4Cl2]
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trans-[Co(NH3)4Cl2]
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Isomerism of Coordination Compounds
⎧Constitutional isomerism
⎪
Isomerism ⎨
⎧Geometric isomerism
⎪Steroisomerism ⎨Optical isomerism
⎩
⎩
Optical isomers (enantiomers): are isomers that are
non-superimposable mirror images of one another.
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Isomerism of Coordination Compounds
⎧Constitutional isomerism
⎪
Isomerism ⎨
⎧Geometric isomerism
⎪Steroisomerism ⎨Optical isomerism
⎩
⎩
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Isomers of Co(en)33+
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Isomerism of Coordination Compounds
cis-[Co(en)2Cl2]
trans-[Co(en)2Cl2]
optical isomers
not optical isomers
chiral
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achiral
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The Optical Isomers of Co(en)2CI2+
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The Optical Isomers of Co(en)2CI2+
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Un-polarized Light Consists of Waves
Vibrating in Many Different Planes
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Color of Coordination Compounds
The color of the different coordination compounds of Co3+
[Co(NH 3 ) 6 ]3+ ,[Co(NH 3 )5 NCS ]2+ ,[Co(NH 3 )5 H 2O ]3+ ,[Co(NH 3 )5Cl ]2+ , trans − [Co(NH 3 ) 4Cl2 ]+
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Color of Coordination Compounds
λabsorption = 510nm
(green and yellow)
The absorption spectrum of [Ti(H2O)6]3+ at 510 nm
(green and yellow), the complex transmits all light except
green and yellow. The complex is purple
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Magnetism of Coordination compounds
• Many transition metal complexes are
paramagnetic (have unpaired electrons)
• An interesting observations ( a d6 metal ion):
– [Co(NH3)6]3+ has no unpaired electrons,
– [CoF6]3- has four unpaired electrons.
???
• A bonding theory to account for both color and
magnetism in transition metal complexes.
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Crystal-Field Theory
Metal ion ⎯⎯⎯→ empty orbitals
provide
Ligands
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⎯⎯⎯
→ electrons pairs
donor
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Structure of Coordination Compounds
The Ligand Arrangements
for Coordination Numbers
2, 4, and 6
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The Hybrid Orbitals Required
for Octahedral and Linear Complex Ions
Octahedral ligand arrangement for Co3+
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The Hybrid Orbitals Required
for Tetrahedral and Square planer
Complex Ions
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An Octahedral Arrangement of Point-Charge
Ligands and the Orientation of the 3d Orbitals
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Bonding in Coordination Compounds
Crystal field
Splitting of
outer d orbital in
octahedral field
Isolated
transition metal
atom
Bonded
transition metal
atom
Crystal field splitting ( ∆): the energy difference between two sets of
d orbitals in a metal atom when ligands are present
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Bonding in Coordination Compounds
Ti3+: a d1 ion
∆ = hν
The absorbance spectrum of Ti(H2O)63+, the maximum
absorption peak at 498nm Shanghai Jiao Tong University
Nov. 2006
Bonding in Coordination Compounds
Spectrochemical Series
I- < Br- < Cl- < OH- < F- < H2O < NH3 < en < CN- < CO
Weak field ligands
Small ∆
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Strong field ligands
Large ∆
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Crystal-Field Theory
I- < Br- < Cl- < OH- < F- < H2O < NH3 < en < CN- < CO
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Crystal-Field Theory
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Bonding in Coordination Compounds
High-spin
Low-spin
High-spin
Low-spin
Orbital Diagrams for high-spin and low-spin octahedral
complex
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Crystal-Field Theory
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Bonding in Coordination Compounds
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Crystal field splitting between d orbitals in
a tetrahedral complex
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Crystal field splitting between d orbitals in
a tetrahedral complex
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The Crystal Field Diagrams for
Octahedral and Tetrahedral
Complexes
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The d Energy Diagrams for
Square-Planar and Linear
Complexes
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Chemistry In Action: Coordination Compounds in Living Systems
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The Heme Complex
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Chemistry In Action: Cisplatin – The Anticancer Drug
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Chlorophyll
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Homework
Chapter 24:
24.02 a to f and K[MnO4]**
24.04 a to f and [Cr(C6H6)2]**
24.06 a, e and tetraammincopper(II)sulfate
24.08 a, b and d
24.10 a and b
24.12**
24.14 a and c
** optional, for extra credits
24.18, 24.28, 24.30, 24.46
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