Chapter 21

Report
Chapter 21
Transition Metals and
Coordination
Chemistry
Chapter 21
Table of Contents
21.1
21.2
21.3
21.4
21.5
21.6
21.7
21.8
The Transition Metals: A Survey
The First-Row Transition Metals
Coordination Compounds
Isomerism
Bonding in Complex Ions: The Localized
Electron Model
The Crystal Field Model
The Biologic Importance of Coordination
Complexes
Metallurgy and Iron and Steel Production
Copyright © Cengage Learning. All rights reserved
2
Section 21.1
The Transition Metals: A Survey
Industry : Fe , Cu , Ti , Ag ,  table 21.1
20.1 The Transition Metals - I
Biosystem : transport , storage , catalyst , 
Return to TOC
Section 21.1
The Transition Metals: A Survey
Transition Metals
• Show great similarities within a given period as
well as within a given vertical group.
(1) General Properties ( Sc → Cu )
a) Great similarities within a period as well as a group
∵ d subshells incomplerely filled.
 distinctive coloring
 formation of paramagnetic compounds
 catalytic behavior
 tendency to form complex ions.
Return to TOC
Copyright © Cengage Learning. All rights reserved
4
Section 21.1
The Transition Metals: A Survey
Return to TOC
Section 21.1
The Transition Metals: A Survey
Cations are often complex ions – species where the transition
metal ion is surrounded by a certain number of ligands
(Lewis bases). The Complex Ion Co(NH3)63+ :
Return to TOC
Copyright © Cengage Learning. All rights reserved
6
Section 21.1
The Transition Metals: A Survey
b) difference :
m.p : W / Hg
Hard / soft : Fe , Ti / Cu , Au , Ag
Reactivity & oxides : Cu / Fe ; Fe2O3 / CrO3
(2) Electron configurations : 4s before 3d
( Cr / Cu )
Table 21.2
p.931
(3) Oxidation states
most common : +2 , +3
( +2 ~ +7 )
more than one oxidation states
Return to TOC
Section 21.1
The Transition Metals: A Survey
Return to TOC
Section 21.1
The Transition Metals: A Survey
(4) Ionization energies
(5) Reduction Potentials
─────→ period, reducing ability ↓ ( Zn , Cr )
∵ Zeff ↑  r ↓ ; IE ↑
Return to TOC
Section 21.2
Atomic
The
First-Row
MassesTransition Metals
• 3d transition metals










Scandium – chemistry strongly resembles lanthanides
Titanium – excellent structural material (light weight)
Vanadium – mostly in alloys with other metals
Chromium – important industrial material
Manganese – production of hard steel
Iron – most abundant heavy metal
Cobalt – alloys with other metals
Nickel – plating more active metals; alloys
Copper – plumbing and electrical applications
Zinc – galvanizing steel
Return to TOC
Copyright © Cengage Learning. All rights reserved
10
Section 21.3
The Mole
Coordination
Compounds
A Coordination Compound
• Typically consists of a complex ion and
counterions (anions or cations as needed to
produce a neutral compound):
[Co(NH3)5Cl]Cl2
[Fe(en)2(NO2)2]2SO4
K3Fe(CN)6
Return to TOC
Copyright © Cengage Learning. All rights reserved
11
Section 21.3
The Mole
Coordination
Compounds
└→
colored & paramagnetic (often)
consists of a complex ion
(1) Coordination compounds are neutral species in which
a small number of molecules or ions surround a
central metal atom or ion.
ex.
[Co(NH3)5Cl]Cl2
complex ion : [Co(NH3)5Cl]2+
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
coordinate covalent bond
Complex ion = metal cation + ligands
e acceptor
e donor
center (one)
surrounding (  2 )
.. ..
..
transion metal
H2O
.. , NH3 , :Cl
.. -
Lewis acid
Lewis base
ionic force
[ Co(NH3)5Cl ]Cl2
central metal
ligands
counter ions
complex ion
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
(2) Coordination number :
The # of donor atoms surrounding
the central metal
The most common : 4 or 6
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
(3) Ligands :
A neutral molecule or ion
having a line pair that can be
used to from a bond to a metal
ion.
monodentate : H2O, NH3
bidentate : en , ox
polydentate : EDTA
 Chelating agents
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
Return to TOC
p. 939, Table 21-13
Section 21.3
The Mole
Coordination
Compounds
(4) Nomenclature :
Rules for naming coordination compounds : p.940
 oxidation number :
Net charge = charges on (central metal + ligands)
[ PtCl6]2-
[Cu(NH3)4]2+
└→ +4
└→ +2
ex. (a)
[Co(NH3)5Cl]Cl2
Pentaammine chloro cobalt(III) chloride
cation
anion
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
Return to TOC
p. 940, Table 21-14
Section 21.3
The Mole
Coordination
Compounds
(4) Nomenclature :
ex. (b)
K3[Fe(CN)6]
potassium hexacyanoferrate (III)
cation
ex. (c)
anion
[Fe(en)2(NO2) 2]2SO4
bis (ethylenediamine) dinitro iron(III) sulfate
cation
anion
Return to TOC
Section 21.3
The Mole
Coordination
Compounds
Exercise
Name the following coordination compounds.
a) [Co(H2O)6]Br3 hexaaquacobalt(III) bromide
b) Na2[PtCl4]
sodiumtetrachloro-platinate(II)
Return to TOC
Copyright © Cengage Learning. All rights reserved
20
Section 21.4
Isomerism
Return to TOC
Copyright © Cengage Learning. All rights reserved
21
Section 21.4
Isomerism
Structural Isomerism
• Coordination Isomerism:
 Composition of the complex ion varies.
 [Cr(NH3)5SO4]Br and [Cr(NH3)5Br]SO4
• Linkage Isomerism:
 Composition of the complex ion is the same,
but the point of attachment of at least one of
the ligands differs.
Return to TOC
Copyright © Cengage Learning. All rights reserved
22
Section 21.4
Isomerism
Linkage Isomerism of
NO2–
Return to TOC
Copyright © Cengage Learning. All rights reserved
23
Section 21.4
Isomerism
Stereoisomerism
• Geometrical Isomerism (cis-trans):
 Atoms or groups of atoms can assume
different positions around a rigid ring or bond.
 Cis – same side (next to each other)
 Trans – opposite sides (across from each
other)
Return to TOC
Copyright © Cengage Learning. All rights reserved
24
Section 21.4
Isomerism
Geometrical (cistrans) Isomerism for
a Square Planar
Compound
a) cis isomer
b) trans isomer
Return to TOC
Copyright © Cengage Learning. All rights reserved
25
Section 21.4
Isomerism
Geometrical (cis-trans) Isomerism for an Octahedral Complex Ion
Return to TOC
Copyright © Cengage Learning. All rights reserved
26
Section 21.4
Isomerism
Stereoisomerism
•
Optical Isomerism:
 Isomers have opposite effects on plane-polarized light.
Return to TOC
Copyright © Cengage Learning. All rights reserved
27
Section 21.4
Isomerism
Optical Activity
•
•
Exhibited by molecules that have nonsuperimposable
mirror images (chiral molecules).
Enantiomers – isomers of nonsuperimposable mirror
images.
Return to TOC
Copyright © Cengage Learning. All rights reserved
28
Section 21.4
Isomerism
Return to TOC
p. 947, Fig. 21-17
Section 21.4
Isomerism
Return to TOC
Section 21.4
Isomerism
Ex. 21.3
at p 948
Return to TOC
p. 948, Fig. 21-13
Section 21.4
Isomerism
Concept Check
Does [Co(en)2Cl2]Cl exhibit geometrical
isomerism?
Yes
Does it exhibit optical isomerism?
Trans form – No
Cis form – Yes
Explain.
Return to TOC
Copyright © Cengage Learning. All rights reserved
32
Section 21.5
Bonding in Complex Ions: The Localized Electron Model
Bonding in Complex Ions
1. The VSEPR model for predicting structure
generally does not work for complex ions.
 However, assume a complex ion with a
coordination number of 6 : octahedral
 two ligands : linear.
 a coordination number of 4 : tetrahedral or
square planar.
2. The interaction between a metal ion and a
ligand : Lewis acid–base reaction
Return to TOC
Copyright © Cengage Learning. All rights reserved
33
Section 21.5
Bonding in Complex Ions: The Localized Electron Model
Hybrid Orbitals for 6,4, and 2 ligands
Return to TOC
Copyright © Cengage Learning. All rights reserved
34
Section 21.6
The Crystal Field Model
• Focuses on the energies of the d orbitals.
Assumptions
1. Ligands are negative point charges.
2. Metal–ligand bonding is entirely ionic:
• strong-field (low–spin):
large splitting of d orbitals
• weak-field (high–spin):
small splitting of d orbitals
Return to TOC
Copyright © Cengage Learning. All rights reserved
35
Section 21.6
The Crystal Field Model
(1) Explains the bonding in complex ions solely in terms of
electrostatic forces.
(2) Two types of electrostatic forces :
attraction : ( M+ ) & ( ligand ion - or ligand : )
repulsion : ( ligand : ) & ( metal e in d orbitals )
(3) Consider : octahedral complexes
●●

●●●
●●●●●
Return to TOC
Section 21.6
The Crystal Field Model
An Octahedral Arrangement of Point-Charge Ligands and the
Orientation of the 3d Orbitals
Return to TOC
Copyright © Cengage Learning. All rights reserved
37
Section 21.6
The Crystal Field Model
The Energies of the 3d Orbitals for a Metal Ion in an Octahedral
Complex
Return to TOC
Copyright © Cengage Learning. All rights reserved
38
Section 21.6
The Crystal Field Model
Possible Electron Arrangements in the Split 3d Orbitals in
an Octahedral Complex of Co3+
•
Strong–field (low–spin):
•
Weak–field (high–spin):
•
Yields the minimum number
of unpaired electrons.
•
Gives the maximum number
of unpaired electrons.
Return to TOC
Copyright © Cengage Learning. All rights reserved
39
Section 21.6
The Crystal Field Model
Spectrochemical Series
• a list of ligands arranged in order of their
abilities to split the d orbital energies
• Strong–field ligands to weak–field ligands.
(large split)
(small split)
CN– > NO2– > en > NH3 > H2O > OH– > F– > Cl– > Br– > I–
• Magnitude of split for a given ligand increases
as the charge on the metal ion increases.
Return to TOC
Copyright © Cengage Learning. All rights reserved
40
Section 21.6
The Crystal Field Model
Color : arise when complexes absorb light in some
portion of the visible spectrum. (Table 21.16)
ex.
[Cu(H2O)6]2+ → blue
 = E = hn
Return to TOC
Section 21.6
The Crystal Field Model
ex. [Ti(H2O)6]3+ max absorption at 498 nm
(6.631034 Js)(3.00108 m / s)
   hn  h 

498nm109 m / nm
 3.991019 J
c
 240kJ / m ol
Return to TOC
Section 21.6
The Crystal Field Model
color of gems
Return to TOC
p. 954, Table 21-17
Section 21.6
The Crystal Field Model
Concept Check
Which of the following are expected to form
colorless octahedral compounds?
Zn2+
Cu+
Fe3+
Fe2+
Cr3+
Cu2+
Mn2+
Ti4+
Ni2+
Ag+
Return to TOC
Copyright © Cengage Learning. All rights reserved
44
Section 21.6
The Crystal Field Model
Tetrahedral Arrangement
• None of the 3d orbitals “point at the ligands”.
 Difference in energy between the split d
orbitals is significantly less.
• d–orbital splitting will be opposite to that for the
octahedral arrangement.
 Weak–field case (high–spin) always applies.
Return to TOC
Copyright © Cengage Learning. All rights reserved
45
Section 21.6
The Crystal Field Model
The d Orbitals in a Tetrahedral Arrangement of Point Charges
Return to TOC
Copyright © Cengage Learning. All rights reserved
46
Section 21.6
The Crystal Field Model
The Crystal Field Diagrams for Octahedral and Tetrahedral Complexes
Tetrahedral Complexes:
Difference in energy between the split d orbitals is significantly less,
Weak–field case (high–spin) always applies for.
Return to TOC
Copyright © Cengage Learning. All rights reserved
47
Section 21.6
The Crystal Field Model
Concept Check
Consider the Crystal Field Model (CFM).
a) Which is lower in energy, d–orbital lobes
pointing toward ligands or between?
Why?
b) The electrons in the d–orbitals – are they
from the metal or the ligands?
Return to TOC
Copyright © Cengage Learning. All rights reserved
48
Section 21.6
The Crystal Field Model
Concept Check
Using the Crystal Field Model, sketch
possible electron arrangements for the
following. Label one sketch as strong field
and one sketch as weak field.
a) Ni(NH3)62+
b) Fe(CN)63–
c) Co(NH3)63+
Return to TOC
Copyright © Cengage Learning. All rights reserved
49
Section 21.6
The Crystal Field Model
Concept Check
A metal ion in a high–spin octahedral
complex has 2 more unpaired electrons
than the same ion does in a low–spin
octahedral complex.
What are some possible metal ions for
which this would be true?
Metal ions would need to be d4 or d7 ions.
Examples include Mn3+, Co2+, and Cr2+.
Return to TOC
Copyright © Cengage Learning. All rights reserved
50
Section 21.6
The Crystal Field Model
Concept Check
Between [Mn(CN)6]3– and [Mn(CN)6]4– which
is more likely to be high spin? Why?
Return to TOC
Copyright © Cengage Learning. All rights reserved
51
Section 21.6
The Crystal Field Model
The d Energy
Diagrams for Square
Planar Complexes
Return to TOC
Copyright © Cengage Learning. All rights reserved
52
Section 21.6
The Crystal Field Model
The d Energy
Diagrams for Linear
Complexes Where the
Ligands Lie Along the
z Axis
Return to TOC
Copyright © Cengage Learning. All rights reserved
53
Section 21.7
The Biologic Importance of Coordination Complexes
• Metal ion complexes are used in humans for the
transport and storage of oxygen, as electrontransfer agents, as catalysts, and as drugs.
Return to TOC
Copyright © Cengage Learning. All rights reserved
54
Section 21.7
The Biologic Importance of Coordination Complexes
First-Row Transition Metals and Their Biological Significance
Return to TOC
Copyright © Cengage Learning. All rights reserved
55
Section 21.7
The Biologic Importance of Coordination Complexes
Biological Importance of Iron
• Plays a central role in almost all living cells.
• Component of hemoglobin and myoglobin.
• Involved in the electron-transport chain.
Return to TOC
Copyright © Cengage Learning. All rights reserved
56
Section 21.7
The Biologic Importance of Coordination Complexes
The Heme Complex
Return to TOC
Copyright © Cengage Learning. All rights reserved
57
Section 21.7
The Biologic Importance of Coordination Complexes
Myoglobin
•
•
The Fe2+ ion is
coordinated to four
nitrogen atoms in the
porphyrin of the heme
(the disk in the figure)
and on nitrogen from
the protein chain.
This leaves a 6th
coordination position
(the W) available for
an oxygen molecule.
Return to TOC
Copyright © Cengage Learning. All rights reserved
58
Section 21.7
The Biologic Importance of Coordination Complexes
Hemoglobin
•
•
two α chains and
two β chains
complex with four
O2 molecules.
Return to TOC
Copyright © Cengage Learning. All rights reserved
59
Section 21.7
The Biologic Importance of Coordination Complexes
About high altitude sickness
Hb(aq) + 4O2(g)
Hb(O2)4(aq)
Return to TOC
p. 959, Fig. 21-22
Section 21.7
The Biologic Importance of Coordination Complexes
About Supercharge Blood: EPO at page 960.
1964 Winter Olympics Gold medal’s winner
The 2009 Tour de France
Return to TOC
p. 960, Fig. 21-24

similar documents