Chapter
20
Transition Elements and Coordination Chemistry
Why Study Coordinated Complexes of Transition metals?
These compounds are used as catalyst in oxidation of organic
compounds and pharmaceutical applications.
Chem 1A Review
Chapter 20
Slide 2
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 3
Chapter 20
Slide 4
ns2np6
ns2np5
ns2np4
ns2np3
ns2np2
ns2np1
d10
d5
d1
ns2
ns1
Electron Configuration and the Periodic Table
4f
5f
Chapter 20
Slide 5
Using periodic table write Noble gas notation
for the following elements:
a)S
b)Fe
[Ne]3s23p4
[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
Slide 6
Chapter 20
Slide 7
Electron Configurations
Chapter 20
Slide 8
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 9
Coordination Compounds
Pt(NH3)2Cl2
“Cisplatin” - a cancer
chemotherapy agent
Co(H2O)62+
Cu(NH3)42+
Chapter 20
Slide 10
[Ni(NH3)6]+2
Coordination
Compounds of Ni2+
[Ni(NH2C2H4NH2)3]+2
Chapter 20
Slide 11
Electron Configurations
Sc (Z = 21): [Ar] 3d1 4s2
Zn (Z = 30): [Ar] 3d10 4s2
Chapter 20
Slide 12
Omit 20.2 - 20.4
Coordination Compounds
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.
H
H
H H H
••
Cl
••
-
Chapter 20
C
••
O
••
••
••
N
••
A ligand has at least one unshared pair
of valence electrons
O
Slide 13
Coordination Compounds
The atom in a ligand that is bound directly to the metal atom is
the donor atom.
••
N
O
H
H H H
H
Ligands with:
one donor atom
two donor atoms
three or more donor atoms
monodentate
bidentate
H2O, NH3, Clethylenediamine
polydentate
EDTA
The number of donor atoms surrounding the central metal atom
in a complex ion is the coordination number.
Chapter 20
Slide 14
Coordination Compounds
Coordination Number: The number of ligand donor
atoms that surround a central metal ion or atom.
Chapter 20
Slide 15
Ligands
02
Chapter 20
Slide 16
Ligands
03
Chapter 20
Slide 17
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 18
Coordination Compounds
bidentate ligand
••
H2N
CH2
CH2
••
NH2
polydentate ligand
(EDTA)
Bidentate and polydentate ligands are called chelating agents
Chapter 20
Slide 19
Naming coordinated complex compounds
What is the Oxidation Numbers of Cu?
+2
Knowing the charge on a complex ion and the charge on each
ligand, one can determine the oxidation number for the metal.
Chapter 20
Slide 20
Oxidation
Number Rules
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.)
Chapter 20
Slide 21
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 22
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 23
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
NO3- has charge of -1
Au = +3
NH3 has no charge
? Cr + 6x(0) + 3x(-1) = 0
Cr = +3
Chapter 20
Slide 24
Oxidation States of the 1st Row Transition Metals
(most stable oxidation numbers are shown in red)
Chapter 20
Slide 25
Learning Check
A complex ion contains a Cr3+ bound to four H2O
molecules and two Cl– ions. Write its formula.
+1
Chapter 20
Slide 26
Coordination Sphere
•
Coordinate bond:
H
H
Ag+(aq) + 2 N
H
H
H
•
H
H
H
N Ag N
H
H
+
H
H
Coordination Sphere: is the central metal and
surrounding ligands. The square brackets separate
the complex from counter ions such as SO42–.
[Ag(NH3)2]2 SO4
Chapter 20
Slide 27
Geometry of Coordination Compounds
Coordination number
2
Structure
Linear
4
Tetrahedral or Square
planar (mostly d8 )
6
Octahedral
Chapter 20
Slide 28
Coordination Number of 7&8
•
Geometry
Pentagonal bipyramid
Hexagonal bipyramid
Coordination Number of 8
Coordination Number of 7
Chapter 20
Slide 29
Coordination Compounds
•
Geometries:
Chapter 20
Slide 30
Nomenclature
Co(H2O)62+
Hexaaquacobalt(II)
H2O as a ligand is aqua
Cu(NH3)42+
Tetraamminecopper(II)
Pt(NH3)2Cl2
diamminedichloroplatinum(II)
NH3 as a ligand is ammine
Systematic naming specifies the type and number of ligands,
the metal, and its oxidation state.
Chapter 20
Slide 31
Ligand’s Names
Chapter 20
01
Slide 32
Chapter 20
Slide 33
Nomenclature
Chapter 20
Slide 34
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 35
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 36
Name the following Complexes:
Pt(
Tris(ethylenediamine)nickel(II)
[Ni(NH2C2H4NH2)3]2+
IrCl(CO)(PPh3)2
Carbonylchlorobis(triphenylphosphine)iridium(I)
Chapter 20
Slide 37
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 38
Constitutional Isomerism
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.
Chapter 20
Slide 39
Linkage Isomerism
NH3 2+
H3N
NO2
sunlight
Co
H3N
NH3
NH3
2+
NH3
H3N
ONO
Co
H3N
NH3
NH3
Such a transformation could be used as an energy
storage device.
Chapter 20
Slide 40
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
Slide 41
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 42
Isomers
•
Geometric Isomers of [Co(NH3)4Cl2]Cl:
Chapter 20
Slide 43
Enantiomers
Chapter 20
Slide 44
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.
•
An object or compound is achiral if it has a
symmetry plane cutting through the middle.
Chapter 20
Slide 45
Enantiomers
Chapter 20
Slide 46
© 2003 John Wiley and Sons Publishers
Unpolarized light.
Chapter 20
Slide 47
plane-polarized light
Plane-polarized light.
Chapter 20
© 2003 John Wiley and Sons Publishers
Slide 48
© 2003 John Wiley and Sons Publishers
Reflected glare is plane-polarized light.
Chapter 20
Slide 49
© 2003 John Wiley and Sons Publishers
Polarizing sunglasses versus glare.
Chapter 20
Slide 50
© 2003 John Wiley and Sons Publishers
Courtesy Andy Washnik
The effect of polarizing lenses on unpolarized light.
Chapter 20
Slide 51
plane-polarized light
Chapter 20
Slide 52
Enantiomers and Molecular
Handedness
Chapter 20
Slide 53
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 54
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 55
Isomers
01
Chapter 20
Slide 56
[Co(NH3)5Br]SO4 (violet),
[Co(NH3)5 SO4]Br (red ).
H3N
H3N
2+
NH3
NO2
Co
NH3
NH3
sunlight
H3N
H3N
2+
NH3
ONO
Co
NH3
NH3
See next slide for Diastereoisomers
Slide 57
Diasteromers
Chapter 20
Slide 58
Bonding in Complexes
•
01
Bonding Theories attempt to account for the
color and magnetic properties
of transition metal complexes.
Ni2+
Co2+
Cu2+
Zn2+
Chapter 20
of [Ni(H2O)6]2+,
[Ni(NH3)6]2+, & [Ni(en)3]2+
•Solutions
Slide 59
Color of Transition Metal Complexes
DE = E2 - E1 = hn =
or
hc
l
hc
l=
DE
Chapter 20
Slide 60
Color of Transition Metal Complexes
Chapter 20
Slide 61
Color of Transition Metal Complexes
Chapter 20
Slide 62
Bonding in Complexes: Valence
Bond Theory
Chapter 20
Slide 63
Bonding in Complexes:
Which empty orbital is metal using for bonding
S, p, d or f ?
Chapter 20
Slide 64
Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained?
4 valence electrons
2 unpaired electrons
Chapter 20
Slide 65
Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained?
4 valence electrons
4 unpaired electrons
Chapter 20
Slide 66
Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained?
4 nonequivalent orbitals
Chapter 20
Slide 67
Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained?
4 equivalent orbitals
Chapter 20
Slide 68
Hybridization and sp3 Hybrid Orbitals
Chapter 20
Slide 69
Hybridization and sp3 Hybrid Orbitals
Chapter 20
Slide 70
Other Kinds of Hybrid Orbitals
Chapter 20
Slide 71
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
Slide 72
The octahedral d2sp3 and sp3d2
Chapter 20
Slide 73
Square Planar geometry of four dsp2
Chapter 20
Slide 74
Bonding in Complexes: Valence
Bond Theory
Experimental results: High Spin
Chapter 20
Slide 75
Bonding in Complexes: Valence
Bond Theory
Experimental results: Low Spin
Chapter 20
Slide 76
High- and Low-Spin Complexes
Experimental results : [CoF6]3- High Spin
[Co(CN)6]3-
High spin: Maxium number of unpaired electron, Paramagnetic
Low spin: Minimum number of unpaired electron
Chapter 20
Slide 77
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 78
Crystal Field Theory
Octahedral Complexes
Directed between
ligands
Directed at
ligands
Chapter 20
Slide 79
Crystal Field Theory
Octahedral Complexes
Chapter 20
Slide 80
Crystal Field Theory
Octahedral Complexes
[Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en)
Chapter 20
(red-violet)
Slide 81
[Ti(H2O)6]3+
Chapter 20
Slide 82
Crystal Field Theory
Octahedral Complexes
The crystal field splitting changes depending on nature
of the legand.
[Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en)
Chapter 20
Slide 83
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
Chapter 20
Slide 84