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Chapter 19. The Transition Metals
19.1 Overview of the Transition Metals
19.2 Coordination Complexes
19.3 Bonding in Coordination Complexes
19.4 Metallurgy
19.5 Applications of Transition Metals
19.6 Transition Metals in Biology
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.1 Overview of the Transition Metals
Learning objective:
Predict periodic properties of transition metals
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.1 Overview of the Transition Metals
Remember that the nd orbital always is more stable than the (n+1)s orbital
Transition metal cations usually have empty (n+1)s orbitals.Inner Transition Metals – lanthanides and actinides
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Physical Properties
Conduct heat and electricityAre malleable and ductile.Most have shiny gray appearance – “silvery”Some exceptions: copper (orange), gold (yellow)Melting points and densities show periodic trend.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Melting Points
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Densities
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Oxidation States
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Representative Transition Metal Compounds
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.2 Coordination Complexes
Learning objective:
Recognize and name transition metal coordination complexes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.2 Coordination Complexes
Ligand – a species that has lone pairs of electrons available to donate to a metal atom or cation. (H2O, NH3, CO, etc..)
Dissolved transition metals usually complex with water molecules.
Usually, the colour associated with the solution comes from the complex formed in water.
Replacing water with another ligand (for instance ammonia) usually results in a colour change.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Complexes of Ni2+
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Colour Changes Indicate Complexation
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Ni(II) Sulphate
NH3 (aq)
[Ni(H2O)6]2+
[Ni(NH3)6]SO4
Solvent Evaporation
Nature of Ligands
The metal ligand bond is formed by the overlap of an empty valence orbital on the metal with the lone pair orbital on the ligand.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Common Ligands
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Common Ligands
Structures of Coordination Complexes
Complexes with coordination number 2 are linear
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Structures of Coordination Complexes
Four coordinate complexes are either square planar or tetrahedral
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Structures of Coordination Complexes
Six coordinate (octahedral) is the most prevalent
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Isomers
Isomers – chemical compounds with the same formula but different structures.
Isomers can have different chemical and physical properties.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Linkage Isomers
Linkage isomers occur when a ligand can bond to a metal using either of two donor atoms.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 – 1 Isomers of Coordination Compounds
Draw ball-and-stick models of all possible isomers of the octahedral compound [Cr(NH3)3Cl3].
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Naming Coordination Compounds
1. As with all salts, name the cation before the anion.2. Within the complex, first name the ligands in alphabetical order, and
then name the metal.3. If the ligand is an anion, add the suffix – o to the stem name (bromo,
Br-). The simplest neutral ligands have special names: aqua (H2O), ammine (NH3), and carbonyl (CO). Other neutral ligands retain their usual names (see Table 19 – 3)
4. Use a Greek prefix (di-, tri-, etc.) to indicate the number of identical ligands. If the name of the ligand already incorporates one of these prefixes, enclose the ligand name in parentheses and use the alternative prefixes bis- (two), tris- (three), and tetrakis- (four). Ignore these numerical prefixes in determining the alphabetical order of the ligands.
5. If the coordination complex is an anion, add the suffix –ate to the stem name of the metal.
6. After the name of the metal, give the oxidation number of the metal in parentheses.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Latin Names of Metals in Anionic Complexes
Example 19 – 2 Naming Coordination Compounds
What is the IUPAC name for each of the following coordination compounds?
(a) [Ni(H2O)6]SO4; (b) [Cr(en)2Cl2]Cl; and (c) K2[CoCl4]
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 - 3
Determine the formulas of the following coordination compounds:
a. fac – Triamminetriiodoruthenium (II)b. cis – Chlorohydridobis(trimethylphosphine)platinum(II)c. Sodium hexacyanoferrate(II)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.3 Bonding in Coordination Complexes
Learning objective:
Use crystal field theory to explain the colour and magnetic properties of complexes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.3 Bonding in Coordination Complexes
Crystal field theory – focuses on electrical interactions between a transition metal ion and its ligands.
Most accurately explains colour and magnetic properties.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Crystal Field Splitting Energy
Not all of the orbitals are at the same energy.
The difference in energy between the orbitals is the crystal field splitting energy, .
The lower energy orbitals are called t2g and the higher energy orbitals are called eg
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Populating the d Orbitals
Must follow Pauli and Hund’s Rule.So the first three electrons will go in
the first three lower energy orbitals. But, where does the next electron go?
Placing it with another electron destabilizes the system, but putting it in the higher energy orbital increases the energy of the system (Pairing Energy)
If the electron is placed in the 4th d-orbital, it is termed high-spin.
If the electron is paired with another electron, it is termed low-spin.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 – 4 Electron Configurations
Draw an energy level diagram and write the d electron configuration of [Pt(en)3]Cl2.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Magnetic Properties of Coordination Complexes
So which energy level is the 4th electron in? The magnetic properties of the complex will depend on this.
The amount of paramagnetism in a molecule depends on the number of unpaired electrons.
This can be measured with a Magnetic Susceptibility Balance.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Magnetic Susceptibility Balance
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 – 5 High- and Low-Spin Complexes
[Fe(NH3)6]2+ is paramagnetic but [Co(NH3)6]3+ is not. Write the electron configuration for each of these metal complexes and draw energy level diagrams showing which has the higher .
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Contributions to Crystal Field Splitting Energy
Ligands play an important factor in the value of .The energetic effects of ligands are explained by the
spectrochemical series.
is also affected by the oxidation state and the position of the metal in the periodic table.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 – 6 Crystal Field Splitting Energy
Arrange the following complexes in order of increasing crystal field splitting:
[Fe(H2O)6]2+, [Fe(H2O)6]3+, [FeCl6]4-, [Ru(H2O)6]3+
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Colour in Coordination Complexes
Colour depends on the splitting energy.When a coordination complex absorbs light, the crystal
field splitting energy must match the energy of the absorbed light.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Relationships Among Wavelength, Colour, and Crystal Field Splitting Energy
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Cr3+ Coordination Complexes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 19 – 7 Determining the Value of
Titanium (III) chloride dissolves in water to give [Ti(H2O)6]3+. This complex ion has the absorption spectrum shown. From the wavelength at which maximum absorption occurs, predict the colour of the solution and calculate in kilojoules per mole.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Square Planar Complexes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Tetrahedral Complexes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.4 Transition Metals In Biology
Learning objective:
Explain the importance of transition metal complexes in biological processes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.4 Transition Metals In Biology
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Metalloproteins
Large macromolecules of amino acids that play three essentials roles:
1. Transport and store molecules Depend on the ability of transition metals to bind and
release ligands
2. Enzymes – catalysts for biochemical reactions, also based on the bind/release mechanism.
3. To serve as redox reagents – ideal due to ability to shuttle between two or more oxidation states.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Haemoglobin
Deoxyhaemoglobin Haemoglobin
Myoglobin
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Also an O2 Transport protein
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Ferritin
Iron Transport Protein
Contains 24 nearly identical polypeptides
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Redox Proteins
Cytochrome c Plastocyanin
Learning objective:
Explain the chemistry of essential steps in the production of pure metals from ores
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.5 Metallurgy
Metallurgy – the production and purification of metals from naturally occurring ore deposits.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.5 Metallurgy
Overview of Metallurgical Processes
Once ore is obtained, contaminants must be removed:
Flotation – a common physical separation process in which ore is crushed and mixed with water to form a thick slurry.
The slurry is mixed with oil and a surfactant.
The polar heads of the surfactant coat the mineral particles, but the nonpolar tails make the particles hydrophobic.
The minerals become trapped in a froth, which is removed from the top.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Leaching
A separation technique which uses solubility properties to separate the components of ores.
Sulphide ores may require roasting (high heat oxidation) before leaching can occur. The roasting process converts the sulphide ores to metal oxides.
Because roasting produces SO2 (a environmental toxin), an aqueous process has been developed. Though the aqueous acidification is more costly, it is preferred over the pollution produced in roasting.
Further refining may be needed to remove more impurities.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Metallurgy of Transition Metals
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Iron and Steel
Iron – the dominant structural material of modern times.
Steel – iron strengthened by additives (700 million tons/year).
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Iron and Steel
Reduction of iron oxides in the blast furnace:
3 Fe2O3 (s) + CO (g) → Fe3O4 (s) + CO2 (g)Fe3O4 (s) + CO (g) → 3 FeO (s) + CO2 (g)FeO (s) + CO (g) → Fe (l) + CO2 (g)
Removal of silica:CaCO3 (s) → CaO (s) + CO2 (g)CaO (s) + SiO2 (s) → CaSiO3 (l)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
“Slag”
Titanium
Purified by first reacting with Cl2 gas to form TiCl4 and then reacting it with molten magnesium to yield Ti in a replacement reaction:
TiO2 (s) + C (s) + 2 Cl2 (g) → TiCl4 (g) + CO2 (g)
TiCl4 (g) + 2 Mg (l) → Ti (s) + 2 MgCl2 (l)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Copper
Most copper ore is less than 1% Cu, so it requires expensive refining including flotation, roasting and electrolysis:
1. Concentrated ore is roasted to yield FeCuS2 (s).
2. 2 FeCuS2 (s) + 3 O2 (g) → 2 CuS (s) + 2 FeO (s) + 2 SO2 (g)
3. CuS (s) → Cu2S (s)
4. 2 Cu2S (l) + 3 O2 (g) → 2 Cu2O (l) + 2 SO2 (g)
2 Cu2O (l) + Cu2S (l) → 6 Cu (l) + SO2 (g)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Impure copper, must be further refined
SO2 (g) waste!
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Electrolytic Copper Production
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Metal Mining in Canada
19.6 Applications of Transition Metals
Learning objective:
Recognize the importance of transition metals in everyday life
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
19.6 Applications of Transition Metals
Titanium – 9th most abundant element High strength, low density When alloyed with Al or Sn, has the highest strength-to-weight ratio of all engineered materials. Major use in construction of
aircraft frames and jet engines. Also resistant to corrosion, thus used in pipes and pumps. TiO2 – most important compound of Ti, chemically inert and nontoxic, used
in cosmetics and toothpaste.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chromium
0.012% of the Earth’s CrustDerived from the Greek word chroma
meaning color - forms a wide variety of compounds with beautiful colors
Main use: metal alloys such as stainless steel (20% Cr)
Cr (VI) is highly toxic.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Copper, Silver and Gold
First three pure metals known to humanity.Cu – produced for electrical wiring and plumbing, also
alloys to form bronze and brass, resists oxidation, toxic in large amounts.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
• Ag – produced as by-product of other metal purifications, used in sterling silver (alloy with Cu), jewelry, batteries, and photography.• Au – used in the manufacture of jewelry, effective in the treatment of rheumatoid arthritis, may have anticancer properties.
Zn and Hg
Found as sulphide ores.Zn – used to protect iron from corrosion, also part of the
brass and bronze alloys, ZnO used as catalyst in the production of rubber and also as a common sunscreen.
Hg – used to extract Ag and Au from their ores, used in fluorescent lights, thermometers, barometers, electrical switches and electrodes.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
The Platinum Metals
Ru, Os, Rh, Ir, Pd and PtFound mingled together in ore depositsMost commonly used as catalysts
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 19 Visual Summary