1. Chapter 22 The d-Block Elements and Coordination Chemistry
General Chemistry: An Integrated Approach Hill, Petrucci, 4th Edition
Chapter 22 The d-Block Elements and Coordination Chemistry
Mark P. Heitz
State University of New York at Brockport
© 2005, Prentice Hall, Inc.

2. Chapter 22: d-Block Elements
On the Periodic Table …
d-block elements contain the transition metals
EOS
Chapter 22: d-Block Elements

3. Relative Orbital Energies in the Fourth-Period Transition Series
EOS
Chapter 22: d-Block Elements

4. Fourth-Period Properties
EOS
Chapter 22: d-Block Elements

5. Chapter 22: d-Block Elements
Atomic Radii
EOS
Chapter 22: d-Block Elements

6. Chapter 22: d-Block Elements
Oxidation Numbers
EOS
Chapter 22: d-Block Elements

7. Chapter 22: d-Block Elements
Scandium
Scandium is rather widely distributed in Earth’s crust, but there is only one mineral from which it is extracted, thortveitite, Sc2Si2O7
Despite its relative rarity, the physical and chemical properties of scandium have been well characterized. Its chemistry is based mostly on the Sc3+ ion
EOS
Scandium properties resemble main group metals, particularly aluminum
Chapter 22: d-Block Elements

8. Chapter 22: d-Block Elements
Titanium
Titanium is the ninth most abundant element in Earth’s crust and the second most abundant transition metal (after iron)
Three desirable properties make titanium a highly useful metal: (1) low density; (2) high structural strength, even at high temperatures; and (3) corrosion resistance
EOS
The most important compound of titanium is the oxide, TiO2, and its most important use is as a white pigment in paints, papers, and plastics
Chapter 22: d-Block Elements

9. Chapter 22: d-Block Elements
Vanadium
Vanadium is reasonably abundant in Earth’s solid crust, ranking nineteenth among the elements
It is mostly obtained as a by-product of the production of uranium from carnotite, K2(UO2)2(VO4)2·3 H2O
Vanadium is of interest because of (1) its use as an alloying element in steel; (2) the catalytic activity of some of its compounds, principally V2O5; and (3) the range of oxidation number in its ions
EOS
The different oxidation states of vanadium gives a variety of distinctive colors
Chapter 22: d-Block Elements

10. Chapter 22: d-Block Elements
Chromium
The most important source of chromium is the mineral chromite, FeCr2O4, or FeO·Cr2O3
In addition to its use in alloys, chromium can be plated onto other metals, generally by electrolysis from a solution containing CrO3 in H2SO4
Dichromate ion, Cr2O72–, is a common oxidizing agent; chromate ion, CrO42–, is a good precipitating agent
EOS
The name chromium is from chromus (color) because its compounds exhibit many colors
Chapter 22: d-Block Elements

11. Chapter 22: d-Block Elements
Manganese
Manganese is obtained mainly from the mineral pyrolusite, MnO2
Ferromanganese alloys are wear resistant and shock resistant and are used for railroad tracks, bulldozers, and road scrapers
Manganese dioxide is the starting point for making most other manganese compounds
EOS
Potassium permanganate, KMnO4, is an important oxidizing agent that is used in both analytical and organic chemistry laboratories
Chapter 22: d-Block Elements

12. The Iron Triad: Fe, Co, and Ni
Iron is the fourth most abundant element in Earth’s crust. Cobalt and nickel are not nearly as common, but they are still sufficiently abundant that their annual production is thousands of tons
All three iron triad elements form 2+ ions
EOS
Ferromagnetism is a much stronger magnetic effect than paramagnetism
Chapter 22: d-Block Elements

13. Ferromagnetism and Paramagnetism
EOS
Chapter 22: d-Block Elements

14. Chapter 22: d-Block Elements
Heme and Hemoglobin
Transition metals are required for life …
EOS
Chapter 22: d-Block Elements

15. Important Metals of Group IB
EOS
Chapter 22: d-Block Elements

16. Chapter 22: d-Block Elements
Zinc
Zinc has many uses, such as in alloys, and is a good electrical conductor
Brass is a copper alloy having from 20 to 45% zinc and small quantities of tin, lead, and iron
Zinc oxidizes in air to form a thin, adherent oxide coating that protects the underlying metal from further corrosion
EOS
Because zinc is more easily oxidized than iron, zinc is used in making galvanized iron
Chapter 22: d-Block Elements

17. Chapter 22: d-Block Elements
Cadmium
Cadmium can substitute for zinc in coating metals for certain applications
Its primary uses are in alloys and as electrodes in batteries
Because of its capacity to absorb neutrons, cadmium is used in control rods in nuclear reactors
Zinc in trace amounts is an essential element for humans; cadmium is quite toxic
EOS
Its effect may be to substitute for zinc in certain enzymes
Chapter 22: d-Block Elements

18. Chapter 22: d-Block Elements
Mercury
Mercury differs from zinc and cadmium in at least six significant ways
Mercury forms few water-soluble compounds and most of its compounds are not hydrated
The physical properties of mercury, especially its metallic and liquid properties and its high density, determine many of its uses
Long-term exposure can present a serious health hazard
EOS
Mercury poisons the body’s systems, in part by interfering with sulfur-containing enzymes
Chapter 22: d-Block Elements

19. The Lanthanide Elements
The elements cerium through lutetium comprise the first series of the f-block and are called the inner transition elements
These elements are frequently called “rare earths,” a name of historical origin but a clear misnomer because several are not rare at all
For many uses, the lanthanides do not have to be separated from one another. A mixture of the lanthanide metals with about 25% La is used in certain steel and magnesium-based alloys. Some of the oxides are used to color glass
EOS
Chapter 22: d-Block Elements

20. Terminology for Complexes
A complex consists of a central atom, which is usually a metal atom or ion, and attached groups called ligands
EOS
The coordination number is the total number of points at which a central atom or ion attaches ligands
Chapter 22: d-Block Elements

21. Terminology for Complexes
The region surrounding the central atom or ion and containing the ligands is called the coordination sphere
EOS
A substance consisting of one or more complexes is called a coordination compound
Chapter 22: d-Block Elements

22. Cobalt(III) Coordination Cmpds
If a complex carries a net electric charge, it is called a complex ion
EOS
Chapter 22: d-Block Elements

23. Chapter 22: d-Block Elements
Ligands
Many metal atoms and ions have empty orbitals that can accommodate electron pairs
EOS
Ligands with one donor atom have just one point of attachment to the central metal atom or ion and are called monodentate ligands
Chapter 22: d-Block Elements

24. Chapter 22: d-Block Elements
Ligands
Polydentate refers to multiple points of attachment by one ligand
EOS
Chapter 22: d-Block Elements

25. Chapter 22: d-Block Elements
Naming Complex Ions
In naming a complex, first name the ligands and then the central metal atom or ion as a single compound word
Name the ligands in alphabetical order based on the first letters of their names and ignoring prefixes
Designate the number of ligands with prefixes
Use the unmodified name of the central metal in a complex cation. In a complex anion, add the ending -ate to the name of the central metal
EOS
Write the names in the order of cation followed by anion
Chapter 22: d-Block Elements

26. Some Metals in Complex Anions
EOS
Chapter 22: d-Block Elements

27. Isomerism in Complex Ions
Structural isomers differ in the ligands that are attached to the central atom or in the donor atoms through which the ligands are bonded
EOS
Geometric isomers differ in the arrangement of the attached ligands, forming either cis- (same side) or trans- (opposite sides) compounds
Chapter 22: d-Block Elements

28. Chapter 22: d-Block Elements
Optical Activity
Optical isomers are isomers that differ in their ability to rotate the plane of polarized light
EOS
Chapter 22: d-Block Elements

29. Chapter 22: d-Block Elements
Optical Activity
Each of the two molecules or ions of an optical isomer is called an enantiomer and each enantiomer rotates the plane-polarized light in opposite directions
EOS
Chapter 22: d-Block Elements

30. Chapter 22: d-Block Elements
Crystal Field Theory
The attractions between a central atom or ion and its ligands are largely electrostatic
EOS
To predict the magnetic properties of a complex ion, its structure and the ability of its ligands to split the d-orbital energy levels must be known
Chapter 22: d-Block Elements

31. Chapter 22: d-Block Elements
d-Level Splitting
EOS
Chapter 22: d-Block Elements

32. Chapter 22: d-Block Elements
Crystal Field Theory
The spectrochemical series shows the relative abilities of some common ligands to split the d-orbital energy levels
EOS
Ligands that produce large energy separations between groups of d orbitals are called “strong field” ligands, and those that produce small separations are “weak field” ligands
Chapter 22: d-Block Elements

33. Chapter 22: d-Block Elements
Color in Complex Ions
Many complex ions are colored because the energy differences between d orbitals match the energies of components of visible light
EOS
Chapter 22: d-Block Elements

34. Effect of Ligands on Colors
EOS
Chapter 22: d-Block Elements

35. Non-visible Transitions
Ions having the following electron configurations have no electron transitions in the energy range of visible light
noble-gas electron configuration
An outer shell with 18 electrons
EOS
An “18 + 2” configuration (for example, Sn2+)
Chapter 22: d-Block Elements

36. Chapter 22: d-Block Elements
Chelates
Chelates generally are much more stable than complexes with monodentate ligands
The increase in entropy during chelation is an important factor in the stabilities of chelates
EDTA (ethylenediaminetetraacetic acid) is commonly used to sequester metal ions in solution
EOS
Chelation therapy is sometimes used to treat heavy metal ion poisoning
Chapter 22: d-Block Elements

37. Chapter 22: d-Block Elements
A Metal–EDTA Complex
EOS
Chapter 22: d-Block Elements

38. Chapter 22: d-Block Elements
Summary of Concepts
All the elements of the d block are metals
Most metals exist in several oxidation states and form many complex ions and colored compounds
The early members in a period in the d block are active metals but later members are less active
Scandium resembles aluminum but is not widely used
The uses of titanium depend on its high strength, low density, and corrosion resistance
EOS
Dichromate and permanganate ions are widely used oxidizing agents
Chapter 22: d-Block Elements

39. Chapter 22: d-Block Elements
Summary (cont’d)
Copper, silver, and gold are much less active than earlier members of their periods
Zinc, cadmium, and mercury are not transition elements; their atoms and ions all have filled d subshells
The central metal atom or ion of a metal complex is a Lewis acid; it forms coordinate covalent bonds by accepting lone-pair electrons from ligands, which are Lewis bases
EOS
Isomerism among complexes is of two general types: structural and optical
Chapter 22: d-Block Elements

40. Chapter 22: d-Block Elements
Summary (cont’d)
Interactions between lone-pair electrons on ligands and electrons in the d orbitals of the central metal atom or ion produce a splitting of the d-orbital energy level
Electron transitions between d orbitals of different energy provide a way for a complex to absorb some wavelength components of visible light and transmit others, giving rise to color
Explanations of the colors and magnetic properties of complexes are facilitated by a special listing of common ligands called the spectrochemical series
EOS
Chapter 22: d-Block Elements