1. Chapter 22 Transition Elements
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2. Transition Elements – d- and f-block
Used in construction and manufacturing (iron), coins (nickel, copper, zinc), ornamental (gold, silver, platinum).
Densest elements (osmium d=22.49 g/cm3, iridium d=22.41g/cm3).
Highest melting point (tungsten, mp=3410oC) and lowest melting point (mercury, mp=-38.9oC).

3. Metal Chemistry
Radioactive elements with atomic number less than 83 (technetium 43; promethium 61).
All elements are solids, but mercury.
Have metallic sheen, conduct electricity and heat.
Are oxidized and form ionic compounds.
Some are essential to living organisms: Cobalt (vitamin B12), iron (hemoglobin and myoglobin), molybdenium and iron (nitrogenase).
Compounds are highly colored and used as pigments: Fe4[Fe(CN)6)3 14 H2O (prussian blue), TiO2 (white).
Ions give color to gemstons: Iron(II) ions give yellow color in citrine and chromium(III) ions produce the red color of a ruby.
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4. Electron Configurations
General:
[noble gas core] nsa (n-1) db
Valance electrons for transition elements reside in the ns and (n-1) d subshells.

5. Reactions
All metals undergo oxidation with oxygen, halogens, aqueous acids.
First the outermost electron is removed, followed by one or more d electrons.
Some generate cations with unpaired electrons = paramagnetism.
Are colored.
For first transition series common oxidation numbers are +2 and +3.
Fe: [Ar]3d64s2
Fe2O3
Fe3+
[Ar]3d5
Fe + O2
Fe + Cl2
Fe + HCl
FeCl3
Fe3+
[Ar]3d5
Fe + Cl2
Fe + HCl
FeCl2 + H2
Fe2+
[Ar]3d6
Fe + O2

6. Trends: Oxidation number
Most common
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7. Trends: Atom Radius
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8. Trends: Density
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9. Trends: Melting Point

10. Metallurgy: Element Sources
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11. Pyrometallurgy Involves high temperature, such as Fe
C and CO used as reducing agents in a blast furnace
Fe2O3 + 3 C ---> 2 Fe + 3 CO
Fe2O3 + 3 CO ---> 2 Fe + 3 CO2
Lime added to remove impurities, chiefly SiO2 SiO2 + CaO ---> CaSiO3
Product is impure cast iron or pig iron
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12. Hydrometallurgy Use aqueous solutions (flotation). Some use bacteria.
Add CuCl2(aq) to ore such as CuFeS2 (chalcopyrite) CuFeS2(s) + 3 CuCl2(aq) --> 4 CuCl(s) + FeCl2(aq) + 2 S(s)
Dissolve CuCl with xs NaCl CuCl(s) + Cl-(aq) --> [CuCl2]-
Cu(I) disproportionates to Cu metal 2 [CuCl2]- --> Cu(s) + CuCl2 (aq) + 2 Cl-
Azurite, 2CuCO3•Cu(OH)2
Native copper
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13. 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. H •• N H O ••
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14. Coordination Chemistry
Pt(NH3)2Cl2
“Cisplatin” - a cancer chemotherapy agent
Co(H2O)62+
Cu(NH3)42+

15. Coordination Chemistry
An iron-porphyrin, the basic unit of hemoglobin
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16. Myoglobin / Hemoglobin
p.1084

17. Coordination Chemistry
Vitamin B12
A naturally occurring cobalt-based compound
Co atom
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18. Coordination Chemistry
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 world’s 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.
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19. Coordination Chemistry
Nickel ion:
coordination compounds

20. Nomenclature [Ni(NH3)6]2+
A Ni2+ ion surrounded by 6, neutral NH3 ligands
Gives coordination complex ion with 2+ charge.
Ligand: monodentate
Coordinate to the metal via a single Lewis base atom.

21. Cis-dichlorobis(ethylenediamine)cobalt(II) chloride
Nomenclature
Inner coordination sphere +
Ligand: polydentate
also chelating ligands
Coordinate with more than one donor atom.
(Bidentate)
Cl-
Co Cl- + 2 neutral ethylenediamine molecules
Cis-dichlorobis(ethylenediamine)cobalt(II) chloride

22. Bidentate Ligands Bipyridine (bipy) Acetylacetone (acac) Oxalate (ox)
Ethylenediamine (en)

23. Acetylacetonate Complexes
Bidentate Ligands
Acetylacetonate Complexes
Commonly called the “acac” ligand. Forms complexes with all transition elements.

24. Multidentate ligands are sometimes called CHELATING ligands
EDTA4- - ethylenediaminetetraacetate ion
Multidentate ligands are sometimes called CHELATING ligands

25. Multidentate Ligands
Co2+ complex of EDTA4-

26. Give the formula of a coordination compound
A Co3+ ion bound to one Cl- ion, one ammonia molecule, and two ethylenediamine (en) molecules.
Determine the net charge (sum the charges of the various components).
Place the formula in brackets and the net charge attached.
[Co(H2NCH2CH2NH2)2(NH3)Cl]2+

27. Determine the metal’s oxidation number and coordination number
Pt(NH3)2(C2O4)
Oxalate: (C2O4)2-
Ammonia: NH3
Pt must be 2+ (oxidation number = +2)
Coordination number = 4 (two from oxalate and each ammonia filling one).
[Co(NH3)5Cl]SO4
Chloride: Cl-
Sulfate: SO42-
Overall complex must be 2+
Co must be 3+ (oxidation number = +3)
Coordination number = 6 (sulfate is not coordinated to the metal).

28. Cis-dichlorobis(ethylenediamine)cobalt(III) chloride
Nomenclature
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 in roman numerals.

29. Nomenclature 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
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30. Nomenclature Tris(ethylenediamine)nickel(II) IrCl(CO)(PPh3)2
[Ni(NH2C2H4NH2)3]2+
Vaska’s compound
Carbonylchlorobis(triphenylphosphine)iridium(I)

31. Geometry of Coordination Compounds
Defined by the arrangement of donor atoms of ligands around the central metal ion.
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32. Isomerim of Coordination Compounds
Two forms of isomerism
Constitutional
Stereoisomerism
Same empirical formula but different atom-to-atom connections
Same atom-to-atom connections but different arrangement in space.
Geometric and Optical

33. Constitutional Isomers
Aldehydes & ketones
3C, 1O, 6H
Coordination isomerism: it is possible to exchange a ligand and the uncoordinated counterion.
Example: [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br
(violet) (red)
Linkage isomerism: it is possible to attach a ligand to the metal through different atoms.
Usually: SCN- and NO2-

34. Constitutional Isomers
sunlight
Such a transformation could be used as an energy storage device.
Pentaamminenitritocobalt(III)
Pentaamminenitrocobalt(III)
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35. Stereoisomerism
One form is commonly called geometric isomerism or cis-trans isomerism. Occurs often with square planar complexes.
cis
trans
Note: there are VERY few tetrahedral complexes. Would not have geometric isomers.

36. Cis and trans-dichlorobis(ethylenediamine)cobalt(II) chloride
Geometric Isomers
Cis and trans-dichlorobis(ethylenediamine)cobalt(II) chloride

37. Geometric Isomers
For octahedral complexes (MX3Y3):
fac isomer has three identical ligands lying at the corners of a triangular face of octahedron (fac=facial).
mer isomer ligands follow a meridian (mer=meridional).
fac isomer
mer isomer

38. Stereoisomers
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 symmetry—will have a non-superimposable mirror image.
Chiral: an asymmetric molecule.
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39. Enantiomers
[Co(NH2C2H4NH2)3]2+

40. Stereoisomers [Co(en)(NH3)2(H2O)Cl]2+
These two isomers have a plane of symmetry. Not chiral.
These two are asymmetric. Have non-superimposable mirror images.

41. These are non-superimposable mirror images:
Stereoisomers
[Co(en)(NH3)2(H2O)Cl]2+
These are non-superimposable mirror images:
enantiomers

42. Bonding 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 ---> ligand field theory
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43. Bonding 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

44. Ligand Field Theory All electrons have the same energy in the free ion
Consider what happens as 6 ligands approach an Fe3+ ion: Orbitals split into two groups as the ligands approach. e g t 2g D0
energy
d(x 2 -y ) dz d xy xz yz
Value of ligand field sppliting: ∆o depends on L: e.g., CN- > H2O > Cl-

45. Octahedral Ligand Field

46. Tetrahedral and Square Planar Ligand Fields

47. Crystal Field Theory Tetrahedral ligand field.
Note that ∆t = 4/9 ∆o and so ∆t is small.
Therefore, tetrahedral complexes tend to absorb “red wavelengths” and be colored blue.
d(x 2 -y ) dz d xy xz yz e t
energy Dt

48. Ways 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 size of ∆o and P, the pairing energy.
P = energy required to create e- pair.

49. Magnetic Properties of Fe2+
High spin
Weak ligand field strength and/or lower Mn+ charge
D0 is smaller than P
[Fe(H2O)6]2+ e g t 2 n r y d ( x - ) z D E s m a l
Paramagnetic e g t 2 D E l a r n y d ( x - ) z
Low spin
Stronger ligand field strength and/or higher Mn+ charge
D0 is larger than P
[Fe(CN)6]4-
Diamagnetic

50. High and Low Spin Octahedral Complexes
High or low spin octahedral complexes only possible for d4, d5, d6, and d7 configurations.

51. Why are complexes colored?
Fe3+
Co2+
Ni2+
Cu2+
Zn2+

52. Why are complexes colored?
Note that color observed is transmitted light.
Red and blue are absorbed

53. Why are complexes colored?
Note that color observed is transmitted light.
Color arises from electron transitions between d orbitals (d-to-d transitions).
Color often not very intense.
Spectra can be complex
d1, d4, d6, and d9 --> 1 absorption band
d2, d3, d7, and d8 --> 3 absorption bands
Spectrochemical series — ligand dependence of light absorbed. The ability to split the d orbitals is determined by spectroscopy.

54. Light absorption by octahedral Co3+ complex( = D0 ) l i h t a b s o d
Excited state
Ground state
Usually excited complex returns to ground state by losing energy, which is observed as heat.

55. Spectrochemical Series
d orbital splitting (value of ∆o) is in the order:
small ∆o large ∆o
I- < Cl- < F- < H2O < NH3 < en < phen < CN- < CO
As ∆ increases, the absorbed light tends to blue, and so the transmitted light tends to red.

56. Other 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+