4910461.ppt

Chapter 20
Transition Elements and Coordination Chemistry

Chapter 20 Slide 2
Chem 1A Review
Why Study Coordinated Complexes of Transition metals?
These compounds are used as catalyst in oxidation of organic
compounds and pharmaceutical applications.

Chapter 20 Slide 3
Order of orbitals (filling) in multi-electron atom
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
< 4f< 5d< 6p< 7s< 5f< 6d< 7p

Chapter 20 Slide 5
ns
1
ns
2
ns
2
np
1
ns
2
np
2
ns
2
np
3
ns
2
np
4
ns
2
np
5
ns
2
np
6
d
1
d
5
d
10
4f
5f
Electron Configuration and the Periodic Table

a)S [Ne]3s23p4
Using periodic table write Noble gas notation
for the following elements:
b)Fe
[Ar] 4s23d6
c)Se [Ar] 4s23d104p4
d)Gd [Xe]6s24f75d1
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
< 4f< 5d< 6p< 7s< 5f< 6d< 7p

Chapter 20 Slide 8
Electron Configurations

Chapter 20 Slide 9
Why Study Coordinated Complexes of Transition metals?
Are used as catalyst in oxidation of organic compounds.
Medicinal applications.
“Cisplatin” - a cancer
chemotherapy agent

Chapter 20 Slide 10
Coordination Compounds
Co(H2O)6
2+
Pt(NH3)2Cl2
Cu(NH3)4
2+
“Cisplatin” - a cancer
chemotherapy agent

Chapter 20 Slide 11
Coordination
Compounds of Ni2+
[Ni(NH2C2H4NH2)3]+2
[Ni(NH3)6]+2

Chapter 20 Slide 12
Electron Configurations
Zn (Z = 30): [Ar] 3d10 4s2
Sc (Z = 21): [Ar] 3d1 4s2

Chapter 20 Slide 13
Many coordination compound consists of a complex ion.
A complex ion contains a central metal cation bonded to one
or more molecules or ions.
The molecules or ions that surround the
metal in a complex ion are called ligands.
A ligand has at least one unshared pair
of valence electrons
H
O
H
••
H
N
H
H
••
•
•
Cl
••
•
•
-
•
•
C O
•
•
Omit 20.2 - 20.4

Chapter 20 Slide 14
The atom in a ligand that is bound directly to the metal atom is
the donor atom.
H
O
H
• •
H
N
H
H
Ligands with:
one donor atom monodentate
two donor atoms bidentate
three or more donor atoms polydentate
H2O, NH3, Cl-
ethylenediamine
EDTA
The number of donor atoms surrounding the central metal atom
in a complex ion is the coordination number.

Chapter 20 Slide 15
Coordination Number: The number of ligand donor
atoms that surround a central metal ion or atom.

Chapter 20 Slide 16
Ligands 02

Chapter 20 Slide 17
Ligands 03

Chapter 20 Slide 18
Poly DentateLigands
• EDTA4– is often used to treat
heavy metal poisoning such
as Hg2+, Pb2+, and Cd2+.
• EDTA4– bonds to Pb2+, which
is excreted by the kidneys as
[Pb(EDTA)]2–.

Chapter 20 Slide 19
H2N CH2 CH2 NH2
•• ••
bidentate ligand polydentate ligand
(EDTA)
Bidentate and polydentate ligands are called chelating agents

Chapter 20 Slide 20
What is the Oxidation Numbers of Cu?
Knowing the charge on a complex ion and the charge on each
ligand, one can determine the oxidation number for the metal.
Naming coordinated complex compounds
+2

Chapter 20 Slide 21
Rule Applies to Statement
1 Elements The oxidation number of an atom in an element is
zero.
2 Monatomic ions The oxidation number of an atom in a monatomic
ion equals the charge of the ion.
3 Oxygen The oxidation number of oxygen is –2 in most of
its compounds. (An exception is O in H2O2 and
other peroxides, where the oxidation number is –
1.)
Oxidation
Number Rules

Chapter 20 Slide 22
Oxidation Number Rules
Rule Applies to Statement
4 Hydrogen +1, it will be -1 when hydrogen comes with metal.
NaH
5 Halogens Fluorine is –1 in all its compounds. Each of the
other halogens is –1 in binary compounds unless
the other element is oxygen.
6 Compounds and
ions
The sum of the oxidation numbers of the atoms in
a compound is zero. The sum in a polyatomic ion
equals the charge on the ion.

Chapter 20 Slide 23
What is the charge on the following Complex,
If the Oxidation number of Cr is +3?
Or, knowing the oxidation number on the metal and the
charges on the ligands, one can calculate the charge on the
complex ion.

Chapter 20 Slide 24
What are the oxidation numbers of the metals in
K[Au(OH)4] and [Cr(NH3)6](NO3)3 ?
OH- has charge of -1
K+ has charge of +1
? Au + 1 + 4x(-1) = 0
Au = +3
NO3
- has charge of -1
NH3 has no charge
? Cr + 6x(0) + 3x(-1) = 0
Cr = +3

Chapter 20 Slide 25
Oxidation States of the 1st Row Transition Metals
(most stable oxidation numbers are shown in red)

Chapter 20 Slide 26
Learning Check
A complex ion contains a Cr3+ bound to four H2O
molecules and two Cl– ions. Write its formula.
+1

Chapter 20 Slide 27
Coordination Sphere
• Coordinate bond:
• Coordination Sphere: is the central metal and
surrounding ligands. The square brackets separate
the complex from counter ions such as SO4
2–.
H
H
H
H
H
H
H
H
+
H
H
H
H
Ag+
(aq) 2 Ag
+
[Ag(NH3)2]2 SO4
N N N

Chapter 20 Slide 28
Geometry of Coordination Compounds
Coordination number Structure
2
4
6
Linear
Tetrahedral or Square
planar (mostly d8 )
Octahedral

Chapter 20 Slide 29
Coordination Number of 7&8
• Geometry
Pentagonal bipyramid Hexagonal bipyramid
Coordination Number of 8
Coordination Number of 7

Chapter 20 Slide 30
• Geometries:

Chapter 20 Slide 31
Nomenclature
Co(H2O)6
2+
Pt(NH3)2Cl2
Cu(NH3)4
2+
Hexaaquacobalt(II)
Tetraamminecopper(II)
diamminedichloroplatinum(II)
H2O as a ligand is aqua
NH3 as a ligand is ammine
Systematic naming specifies the type and number of ligands,
the metal, and its oxidation state.

Chapter 20 Slide 32
Ligand’s Names 01

Chapter 20 Slide 34
Nomenclature

Chapter 20 Slide 35
Nomenclature
• Systematic naming follows IUPAC rules:
• If compound is a salt, name cation first and then the
anion, just as in naming simple salts.
• In naming a complex ion or neutral complex, name
ligands first and then the metal.
• If the complex contains more than one ligand of a
particular type, indicate the number with the appropriate
Greek prefix: di–, tri–, tetra–, penta–, hexa–.

Chapter 20 Slide 36
Nomenclature
• If the name of a ligand itself contains a Greek prefix,
(ethylenediamine or triphenylphosphine) put the ligand name in
parentheses and use: bis (2), tris (3), or tetrakis (4).
• Use a Roman numeral in parentheses, immediately following the
name of the metal, to indicate the metal’s oxidation state.
• In naming the metal, use the ending –ate if metal is in an anionic
complex.

Chapter 20 Slide 37
Name the following Complexes:
Pt(
Tris(ethylenediamine)nickel(II)
IrCl(CO)(PPh3)2
Carbonylchlorobis(triphenylphosphine)iridium(I)
[Ni(NH2C2H4NH2)3]2+

Chapter 20 Slide 38
What is the systematic name of
[Cr(H2O)4Cl2]Cl ?
tetraaquadichlorochromium(III) chloride
Write the formula of
tris(ethylenediamine)cobalt(II) sulfate
[Co(en)3]SO4

Chapter 20 Slide 39
1. Constitutional Isomers: Have different bonds
among their constituent atoms.
• Ionization Isomers :
[Co(NH3)5Br]SO4 (violet compound with Co–Br bond),
[Co(NH3)5 SO4]Br (red compound with Co–SO4 bond).
• Linkage Isomers form when a ligand can bond through
two different donor atoms. Consider [Co(NH3)5NO2]2+
which is yellow with the Co–NO2 bond and red with the
Co–ONO bond.
Constitutional Isomerism

Chapter 20 Slide 40
Linkage Isomerism
Co
H3N
H3N NO2
NH3
NH3
NH3
2+
Co
H3N
H3N ONO
NH3
NH3
NH3
2+
sunlight
Such a transformation could be used as an energy
storage device.

2.Stereoisomers
• Geometric Isomers of Pt(NH3)2Cl2: In the cis
isomer, atoms are on the same side. In the trans
isomer, atoms are on opposite sides.
DNA-damaging antitumor agents Inactive

Chapter 20 Slide 42
2.Stereoisomers
Geometric Isomers have the same connections
among atoms but different spatial orientations of
the metal–ligand bonds.
a)cis isomers have identical ligands in adjacent corners
of a square.
b)trans isomers have identical ligands across the
corners from each other.

Chapter 20 Slide 43
• Geometric Isomers of [Co(NH3)4Cl2]Cl:
Isomers

Chapter 20 Slide 44
Enantiomers

Chapter 20 Slide 45
• An object or compound is achiral if it has a
symmetry plane cutting through the middle.
Enantiomers
•Enantiomers are stereoisomers of molecules or ions
that are nonidentical mirror images of each other.
•Objects that have “handedness” are said to be chiral,
and objects that lack “handedness” are said to be achiral.

Chapter 20 Slide 46
Enantiomers

Chapter 20 Slide 47
Unpolarized light.
© 2003 John Wiley and Sons Publishers

Chapter 20 Slide 48
Plane-polarized light.
plane-polarized light

Chapter 20 Slide 49
Reflected glare is plane-polarized light.

Chapter 20 Slide 50
Polarizing sunglasses versus glare.

Chapter 20 Slide 51
The effect of polarizing lenses on unpolarized light.
Courtesy Andy Washnik

Chapter 20 Slide 52
plane-polarized light

Chapter 20 Slide 53
Enantiomers and Molecular
Handedness

Chapter 20 Slide 54
Enantiomers
Enantiomers have identical properties except for their
reaction with other chiral substances and their effect
on plane-polarized light.
•Enantiomers are often called optical isomers; their
effect on plane-polarized light can be measured with
a polarimeter.

Chapter 20 Slide 55
Enantiomers
• Plane-polarized light is obtained by passing
ordinary light through a polarizing filter.
• In a polarimeter the plane-polarized light is passed
through a chiral solution and the polarization plane
measured with an analyzing filter.
• If the plane rotates to the right it is dextrorotatory.
• If the plane rotates to the left it is levorotatory.
• Equal amounts of each are racemic.

Chapter 20 Slide 56
Isomers 01

Co
H3N
H3N NO2
NH3
NH3
NH3
2+
Co
H3N
H3N ONO
NH3
NH3
NH3
2+
sunlight
[Co(NH3)5Br]SO4 (violet),
[Co(NH3)5 SO4]Br (red ).
See next slide for Diastereoisomers

Chapter 20 Slide 58
Diasteromers

Chapter 20 Slide 59
Bonding in Complexes 01
• Bonding Theories attempt to account for the
color and magnetic properties
of transition metal complexes.
Ni2+ Cu2+
Zn2+
Co2+
•Solutions of [Ni(H2O)6]2+,
[Ni(NH3)6]2+, & [Ni(en)3]2+

Chapter 20 Slide 60
Color of Transition Metal Complexes
or
DE
hc
l =
DE = E2 - E1 = hn =
l
hc

Chapter 20 Slide 61

Chapter 20 Slide 62

Chapter 20 Slide 63
Bonding in Complexes: Valence
Bond Theory

Chapter 20 Slide 64
Bonding in Complexes:
Which empty orbital is metal using for bonding
S, p, d or f ?

Chapter 20 Slide 65
Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained?
4 valence electrons
2 unpaired electrons

Chapter 20 Slide 66
4 valence electrons
4 unpaired electrons

Chapter 20 Slide 67
4 nonequivalent orbitals

Chapter 20 Slide 68
4 equivalent orbitals

Chapter 20 Slide 69

Chapter 20 Slide 70

Chapter 20 Slide 71
Other Kinds of Hybrid Orbitals

Hybrid Orbitals in Coordinated Complexes
We should look at magnetic property of the complex
to see if they are high or low spin. Then we could
decide whether they are using d2sp3 or sp3d2 hybrid

Chapter 20 Slide 73
The octahedral d2sp3 and sp3d2

Chapter 20 Slide 74
Square Planar geometry of four dsp2

Chapter 20 Slide 75
Bond Theory
Experimental results: High Spin

Chapter 20 Slide 76
Bond Theory
Experimental results: Low Spin

Chapter 20 Slide 77
High- and Low-Spin Complexes
Low spin: Minimum number of unpaired electron
High spin: Maxium number of unpaired electron, Paramagnetic
Experimental results : High Spin
[CoF6]3-
[Co(CN)6]3-

Chapter 20 Slide 78
Crystal Field Theory
Crystal Field Theory:
Effect of charges of ligand on transition metal
d-electrons.
A model that views the bonding in complexes as
arising from electrostatic interactions and considers
the effect of the ligand charges on the energies of
the metal ion d orbitals.

Chapter 20 Slide 79
Directed at
ligands
Directed between
ligands
Octahedral Complexes

Chapter 20 Slide 80

Chapter 20 Slide 81
[Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en)
(red-violet)

[Ti(H2O)6]3+
Chapter 20 Slide 82

Chapter 20 Slide 83
[Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en)
The crystal field splitting changes depending on nature
of the legand.

Chapter 20 Slide 84
The absorption maximum for the complex ion
[Co(NH3)6]3+ occurs at 470 nm. What is the color of
the complex and what is the crystal field splitting in
kJ/mol?
DE = hn
hc
l
= = 4.23 x 10-19 J
DE (kJ/mol) ?
= 255 kJ/mol

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