Transcript Ch. 21 PP - Lemon Bay High School

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
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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.
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Section 21.1
The Transition Metals: A Survey
The Position of the Transition Elements on the Periodic Table
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Section 21.1
The Transition Metals: A Survey
Forming Ionic Compounds
• More than one oxidation state is often found.
• Cations are often complex ions – species where
the transition metal ion is surrounded by a
certain number of ligands (Lewis bases).
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Section 21.1
The Transition Metals: A Survey
The Complex Ion Co(NH3)63+
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Section 21.1
The Transition Metals: A Survey
Ionic Compounds with Transition Metals
• Most compounds are colored because the
transition metal ion in the complex ion can
absorb visible light of specific wavelengths.
• Many compounds are paramagnetic.
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Section 21.1
The Transition Metals: A Survey
Electron Configurations
• Example
 V: [Ar]4s23d3
• Exceptions: Cr and Cu
 Cr: [Ar]4s13d5
 Cu: [Ar]4s13d10
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Section 21.1
The Transition Metals: A Survey
Electron Configurations
• First-row transition metal ions do not have 4s
electrons.
 Energy of the 3d orbitals is less than that of
the 4s orbital.
Ti: [Ar]4s23d2
Ti3+: [Ar]3d1
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Section 21.1
The Transition Metals: A Survey
Concept Check
What is the expected electron configuration of
Sc+?
Explain.
[Ar]3d2
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Section 21.1
The Transition Metals: A Survey
Plots of the First (Red Dots) and Third (Blue Dots) Ionization
Energies for the First-Row Transition Metals
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Section 21.1
The Transition Metals: A Survey
Atomic Radii of the 3d, 4d, and 5d Transition Series
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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
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Oxidation States and Species for Vanadium in Aqueous Solution
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Typical Chromium Compounds
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Some Compounds of Manganese in Its Most Common Oxidation
States
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Typical Compounds
of Iron
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Typical Compounds
of Cobalt
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Typical Compounds
of Nickel
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Typical Compounds of Copper
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Section 21.2
Atomic
The
First-Row
MassesTransition Metals
Alloys Containing Copper
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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
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Section 21.3
The Mole
Coordination
Compounds
Coordination Number
• Number of bonds formed between the metal ion
and the ligands in the complex ion.
 6 and 4 (most common)
 2 and 8 (least common)
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Section 21.3
The Mole
Coordination
Compounds
Ligands
• Neutral molecule or ion having a lone electron
pair that can be used to form a bond to a metal
ion.
 Monodentate ligand – one bond to a metal
ion
 Bidentate ligand (chelate) – two bonds to a
metal ion
 Polydentate ligand – more than two bonds to
a metal ion
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Section 21.3
The Mole
Coordination
Compounds
Coordinate Covalent Bond
• Bond resulting from the interaction between a
Lewis base (the ligand) and a Lewis acid (the
metal ion).
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Section 21.3
The Mole
Coordination
Compounds
The Bidentate Ligand
Ethylenediamine and
the Monodentate
Ligand Ammonia
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Section 21.3
The Mole
Coordination
Compounds
The Coordination of
EDTA with a 2+ Metal
Ion
ethylenediaminetetraacetate
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Section 21.3
The Mole
Coordination
Compounds
Rules for Naming Coordination Compounds
[Co(NH3)5Cl]Cl2
1. Cation is named before the anion.
“chloride” goes last (the counterion)
2. Ligands are named before the metal ion.
ammonia (ammine) and chlorine
(chloro) named before cobalt
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Section 21.3
The Mole
Coordination
Compounds
Rules for Naming Coordination Compounds
[Co(NH3)5Cl]Cl2
3. For negatively charged ligands, an “o” is added
to the root name of an anion (such as fluoro,
bromo, chloro, etc.).
4. The prefixes mono-, di-, tri-, etc., are used to
denote the number of simple ligands.
penta ammine
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Section 21.3
The Mole
Coordination
Compounds
Rules for Naming Coordination Compounds
[Co(NH3)5Cl]Cl2
5. The oxidation state of the central metal ion is
designated by a Roman numeral:
cobalt (III)
6. When more than one type of ligand is present,
they are named alphabetically:
pentaamminechloro
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Section 21.3
The Mole
Coordination
Compounds
Rules for Naming Coordination Compounds
[Co(NH3)5Cl]Cl2
7. If the complex ion has a negative charge, the
suffix “ate” is added to the name of the metal.
The correct name is:
pentaamminechlorocobalt(III) chloride
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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)
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Section 21.4
Isomerism
Some Classes of Isomers
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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.
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Section 21.4
Isomerism
Linkage Isomerism of
NO2–
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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)
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Section 21.4
Isomerism
Geometrical (cistrans) Isomerism for
a Square Planar
Compound
a) cis isomer
b) trans isomer
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Section 21.4
Isomerism
Geometrical (cis-trans) Isomerism for an Octahedral Complex Ion
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Section 21.4
Isomerism
Stereoisomerism
• Optical Isomerism:
 Isomers have opposite effects on planepolarized light.
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Section 21.4
Isomerism
Unpolarized Light Consists of Waves Vibrating in Many Different
Planes
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Section 21.4
Isomerism
The Rotation of the Plane of Polarized Light by an Optically Active
Substance
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Section 21.4
Isomerism
Optical Activity
• Exhibited by molecules that have
nonsuperimposable mirror images (chiral
molecules).
• Enantiomers – isomers of nonsuperimposable
mirror images.
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Section 21.4
Isomerism
A Human Hand Exhibits a Nonsuperimposable Mirror Image
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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.
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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 will have an
octahedral arrangement of ligands.
 And, assume complexes with two ligands will
be linear.
 But, complexes with a coordination number
of 4 can be either tetrahedral or square
planar.
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Section 21.5
Bonding in Complex Ions: The Localized Electron Model
Bonding in Complex Ions
2. The interaction between a metal ion and a
ligand can be viewed as a Lewis acid–base
reaction with the ligand donating a lone pair of
electrons to an empty orbital of the metal ion to
form a coordinate covalent bond.
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Section 21.5
Bonding in Complex Ions: The Localized Electron Model
The Interaction Between a Metal Ion and a Ligand Can Be Viewed
as a Lewis Acid-Base Reaction
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Section 21.5
Bonding in Complex Ions: The Localized Electron Model
Hybrid Orbitals on Co3+ Can Accept an Electron Pair from Each NH3
Ligand
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Section 21.5
Bonding in Complex Ions: The Localized Electron Model
The Hybrid Orbitals Required for Tetrahedral, Square Planar, and
Linear Complex Ions
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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
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Section 21.6
The Crystal Field Model
Octahedral Complexes
• d z and d x  y point their lobes directly at the
point-charge ligands.
• d xz , d yz ,and d xy point their lobes between the
point charges.
2
2
2
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Section 21.6
The Crystal Field Model
An Octahedral Arrangement of Point-Charge Ligands and the
Orientation of the 3d Orbitals
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Section 21.6
The Crystal Field Model
Which Type of Orbital is Lower in Energy?
• Because the negative point-charge ligands
repel negatively charged electrons, the
electrons will first fill the d orbitals farthest from
the ligands to minimize repulsions.
• The d xz , d yz ,and d xy orbitals are at a lower energy
in the octahedral complex than are the
d z and d x  y orbitals.
2
2
2
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Section 21.6
The Crystal Field Model
The Energies of the 3d Orbitals for a Metal Ion in an Octahedral
Complex
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Section 21.6
The Crystal Field Model
Possible Electron
Arrangements in the
Split 3d Orbitals in an
Octahedral Complex
of Co3+
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Section 21.6
The Crystal Field Model
Magnetic Properties
• Strong–field (low–spin):
 Yields the minimum number of unpaired
electrons.
• Weak–field (high–spin):
 Gives the maximum number of unpaired
electrons.
• Hund’s rule still applies.
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Section 21.6
The Crystal Field Model
Spectrochemical Series
• 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.
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Section 21.6
The Crystal Field Model
Complex Ion Colors
• When a substance absorbs certain wavelengths
of light in the visible region, the color of the
substance is determined by the wavelengths of
visible light that remain.
 Substance exhibits the color complementary
to those absorbed.
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Section 21.6
The Crystal Field Model
Complex Ion Colors
• The ligands coordinated to a given metal ion
determine the size of the d–orbital splitting, thus
the color changes as the ligands are changed.
• A change in splitting means a change in the
wavelength of light needed to transfer electrons
between the t2g and eg orbitals.
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Section 21.6
The Crystal Field Model
Absorbtion of Visible Light by the Complex Ion Ti(H2O)63+
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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+
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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.
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Section 21.6
The Crystal Field Model
The d Orbitals in a Tetrahedral Arrangement of Point Charges
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Section 21.6
The Crystal Field Model
The Crystal Field Diagrams for Octahedral and Tetrahedral
Complexes
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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?
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Section 21.6
The Crystal Field Model
Concept Check
Consider the Crystal Field Model (CFM).
c) Why would electrons choose to pair up in
d–orbitals instead of being in separate
orbitals?
d) Why is the predicted splitting in
tetrahedral complexes smaller than in
octahedral complexes?
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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+
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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+.
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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?
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Section 21.6
The Crystal Field Model
The d Energy
Diagrams for Square
Planar Complexes
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Section 21.6
The Crystal Field Model
The d Energy
Diagrams for Linear
Complexes Where the
Ligands Lie Along the
z Axis
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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.
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Section 21.7
The Biologic Importance of Coordination Complexes
First-Row Transition Metals and Their Biological Significance
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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.
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Section 21.7
The Biologic Importance of Coordination Complexes
The Heme Complex
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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.
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Section 21.7
The Biologic Importance of Coordination Complexes
Hemoglobin
•
•
Each hemoglobin
has two α chains
and two β chains,
each with a heme
complex near the
center.
Each hemoglobin
molecule can
complex with four
O2 molecules.
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Section 21.8
Metallurgy and Iron and Steel Production
Metallurgy
• Process of separating a metal from its ore and
preparing it for use.
• Steps:
 Mining
 Pretreatment of the ore
 Reduction to the free metal
 Purification of the metal (refining)
 Alloying
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Section 21.8
Metallurgy and Iron and Steel Production
The Blast Furnace
Used In the
Production of Iron
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Section 21.8
Metallurgy and Iron and Steel Production
A Schematic of the Open Hearth Process for Steelmaking
CaCO3 
 CaO + CO2
Heat
4Al + 3O2 
 2Al2O3
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Section 21.8
Metallurgy and Iron and Steel Production
The Basic Oxygen Process for Steelmaking
•
•
Much faster.
Exothermic oxidation
reactions proceed so
rapidly that they produce
enough heat to raise the
temperature nearly to the
boiling point of iron
without an external heat
source.
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