Title: Chapter 22 The Chemistry of the Transition Elements
1Chapter 22The Chemistry of the Transition
Elements
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3Transition Metal Chemistry
4Transition Metal Chemistry
5Gems Minerals
- Citrine and amethyst are quartz (SiO2) with a
trace of cationic iron that gives rise to the
color.
6Gems Minerals
7Reactions Transition Metals
8Periodic Trends Atom Radius
9Periodic Trends Density
10Periodic Trends Melting Point
11Periodic Trends Oxidation Numbers
12Metallurgy Element Sources
13Pyrometallurgy
- Involves high temperature, such as Fe
- C and CO used as reducing agents in a blast
furnace - Fe2O3 3 C f 2 Fe 3 CO
- Fe2O3 3 CO f 2 Fe 3 CO2
- Lime added to remove impurities, chiefly
SiO2 SiO2 CaO f CaSiO3 - Product is impure cast iron or pig iron
14MetallurgyBlast Furnace
See Active Figure 22.8
15MetallurgyBlast Furnace
Molten iron is poured from a basic oxygen furnace.
16Metallurgy Copper Ores
Azurite, 2CuCO3Cu(OH)2
Native copper
17Metallurgy Hydrometallurgy
- Uses aqueous solutions
- Add CuCl2(aq) to ore such as CuFeS2
(chalcopyrite)CuFeS2 (s) 3 CuCl2 (aq) f 4
CuCl(s) FeCl2 (aq) 2 S(s) - Dissolve CuCl with xs NaClCuCl(s) Cl-(aq) f
CuCl2- - Cu(I) disproportionates to Cu metal2 CuCl2- f
Cu(s) CuCl2 (aq) 2 Cl-
18Electrolytic Refining of Cu
SeeFigure 22.11
19Coordination Chemistry
- Coordination compounds
- combination of two or more atoms, ions, or
molecules where a bond is formed by sharing a
pair of electrons originally associated with only
one of the compounds.
20Coordination Chemistry
Pt(NH3)2Cl2
Cisplatin - a cancer chemotherapy agent
Co(H2O)62
Cu(NH3)42
21Coordination Chemistry
An iron-porphyrin, the basic unit of hemoglobin
22Vitamin B12
A naturally occurring cobalt-based compound
23Nitrogenase
- Biological nitrogen fixation contributes about
half of total nitrogen input to global
agriculture, remainder from Haber process. - To produce the H2 for the Haber process consumes
about 1 of the worlds total energy. - A similar process requiring only atmospheric T
and P is carried out by N-fixing bacteria, many
of which live in symbiotic association with
legumes. - N-fixing bacteria use the enzyme nitrogenase
transforms N2 into NH3. - Nitrogenase consists of 2 metalloproteins one
with Fe and the other with Fe and Mo.
24Coordination Compounds of Ni2
25Nomenclature
Ni(NH3)62 A Ni2 ion surrounded by 6, neutral
NH3 ligands Gives coordination complex ion with
2 charge.
26Nomenclature
Inner coordination sphere
Ligand monodentate
Cl-
Ligand bidentate
Co3 2 Cl- 2 neutral ethylenediamine molecules
Cis-dichlorobis(ethylenediamine)cobalt(II)
chloride
27Common Bidentate Ligands
28Acetylacetonate Complexes
Commonly called the acac ligand. Forms
complexes with all transition elements.
29Multidentate Ligands
EDTA4- - ethylenediaminetetraacetate ion
Multidentate ligands are sometimes called
CHELATING ligands
30Multidentate Ligands
Co2 complex of EDTA4-
31Nomenclature
Cis-dichlorobis(ethylenediamine)cobalt(III)
chloride
1. Positive ions named first 2. Ligand names
arranged alphabetically 3. Prefixes -- di, tri,
tetra for simple ligands bis, tris, tetrakis for
complex ligands 4. If M is in cation, name of
metal is used 5. If M is in anion, then use
suffix -ate CuCl42- tetrachlorocuprate 6.
Oxidation no. of metal ion indicated
32Nomenclature
Co(H2O)62
Hexaaquacobalt(II)
Cu(NH3)42
H2O as a ligand is aqua
Tetraamminecopper(II)
Pt(NH3)2Cl2
diamminedichloroplatinum(II)
NH3 as a ligand is ammine
33Nomenclature
Tris(ethylenediamine)nickel(II)
Pt(
Ni(NH2C2H4NH2)32
IrCl(CO)(PPh3)2
Vaskas compound
Carbonylchlorobis(triphenylphosphine)iridium(I)
34Structures of Coordination Compounds
35Isomerism
- Two forms of isomerism
- Constitutional
- Stereoisomerism
- Constitutional
- Same empirical formula but different atom-to-atom
connections - Stereoisomerism
- Same atom-to-atom connections but different
arrangement in space.
36Constitutional Isomerism
Aldehydes ketones
Peyrones chloride Pt(NH3) 2Cl2 Magnuss green
salt Pt(NH3)4PtCl4
37Linkage Isomerism
Such a transformation could be used as an energy
storage device.
38Stereoisomerism
- One form is commonly called geometric isomerism
or cis-trans isomerism. Occurs often with square
planar complexes.
Note there are VERY few tetrahedral complexes.
Would not have geometric isomers.
39Geometric Isomerism
Cis and trans-dichlorobis(ethylenediamine)cobalt(I
I) chloride
40Geometric Isomerism
Mer isomer
Fac isomer
41Stereoisomerism
- Enantiomers stereoisomers that have a
non-superimposable mirror image - Diastereoisomers stereoisomers that do not have
a non-superimposable mirror image (cis-trans
isomers) - Asymmetric lacking in symmetrywill have a
non-superimposable mirror image - Chiral an asymmetric molecule
42An Enantiomeric Pair
Co(NH2C2H4NH2)32
43StereoisomerismCo(en)(NH3)2(H2O)Cl2
These two isomers have a plane of symmetry. Not
chiral.
These two are asymmetric. Have non-superimposable
mirror images.
44Stereoisomerism
These are non-superimposable mirror images
Co(en)(NH3)2(H2O)Cl2
45Bonding in Coordination Compounds
- Model must explain
- Basic bonding between M and ligand
- Color and color changes
- Magnetic behavior
- Structure
- Two models available
- Molecular orbital
- Electrostatic crystal field theory
- Combination of the two f ligand field theory
46Bonding in Coordination Compounds
- As ligands L approach the metal ion M,
- L/M orbital overlap occurs
- L/M electron repulsion occurs
- Crystal field theory focuses on the latter, while
MO theory takes both into account
47Bonding in Coordination Compounds
48Crystal Field Theory
- Consider what happens as 6 ligands approach an
Fe3 ion
All electrons have the same energy in the free ion
Orbitals split into two groups as the ligands
approach.
Value of ?o depends on ligand e.g., H2O gt Cl-
49Octahedral Ligand Field
50Tetrahedral Square Planar Ligand Field
51Crystal Field Theory
- Tetrahedral ligand field
- Note that ?t 4/9 ?o and so ?t is small
- Therefore, tetrahedral complexes tend to blue end
of spectrum
52Ways to Distribute Electrons
- For 4 to 7 d electrons in octahedral complexes,
there are two ways to distribute the electrons. - High spin maximum number of unpaired e-
- Low spin minimum number of unpaired e-
- Depends on size of ?o and P, the pairing energy.
- P energy required to create e- pair.
53Magnetic Properties/Fe2
- High spin
- Weak ligand field strength and/or lower Mn
charge - Higher P possible?
Paramagnetic
- Low spin
- Stronger ligand field strength and/or higher Mn
charge - Lower P possible?
Diamagnetic
54High and Low Spin Octahedral ComplexesSee Figure
22.25
High or low spin octahedral complexes only
possible for d4, d5, d6, and d7 configurations.
55Crystal Field Theory
- Why are complexes colored?
Fe3
Co2
Cu2
Ni2
Zn2
56Crystal Field Theory
- Why are complexes colored?
- Note that color observed for Ni2 in water is
transmitted light
57Crystal Field Theory
- Why are complexes colored?
- Note that color observed is transmitted light
58Crystal Field Theory
- Why are complexes colored?
- Note that color observed is transmitted light
- Color arises from electron transitions between d
orbitals - Color often not very intense
- Spectra can be complex
- d1, d4, d6, and d9 --gt 1 absorption band
- d2, d3, d7, and d8 --gt 3 absorption bands
- Spectrochemical series ligand dependence of
light absorbed.
59Light Absorption by Octahedral Co3 Complex
Ground state
Excited state
Usually excited complex returns to ground state
by losing energy, which is observed as heat.
60Spectrochemical Series
- d orbital splitting (value of ?o) is in the
orderI- lt Cl- lt F- lt H2O lt NH3 lt en lt phen lt CN-
lt CO
As ? increases, the absorbed light tends to blue,
and so the transmitted light tends to red.
61Other Ways to Induce Color
- Intervalent transfer bands (IT) between ion of
adjacent oxidation number. - Aquamarine and kyanite are examples
- Prussian blue
- Color centers
- Amethyst has Fe4
- When amethyst is heated, it forms citrine as Fe4
is reduced to Fe3
Prussian blue contains Fe3 and Fe2