John C Kotz Paul M Treichel John Townsend

John C. Kotz Paul M. Treichel John Townsend http: //academic. cengage. com/kotz Chapter 22 The Chemistry of the Transition Elements John C. Kotz • State University of New York, College at Oneonta

2 Important – Read Before Using Slides in Class Instructor: This Power. Point presentation contains photos and figures from the text, as well as selected animations and videos. For animations and videos to run properly, we recommend that you run this Power. Point presentation from the Power. Lecture disc inserted in your computer. Also, for the mathematical symbols to display properly, you must install the supplied font called “Symb_chm, ” supplied as a cross-platform True. Type font in the “Font_for_Lectures” folder in the "Media" folder on this disc. If you prefer to customize the presentation or run it without the Power. Lecture disc inserted, the animations and videos will only run properly if you also copy the associated animation and video files for each chapter onto your computer. Follow these steps: 1. Go to the disc drive directory containing the Power. Lecture disc, and then to the “Media” folder, and then to the “Power. Point_Lectures” folder. 2. In the “Power. Point_Lectures” folder, copy the entire chapter folder to your computer. Chapter folders are named “chapter 1”, “chapter 2”, etc. Each chapter folder contains the Power. Point Lecture file as well as the animation and video files. For assistance with installing the fonts or copying the animations and video files, please visit our Technical Support at http: //academic. cengage. com/support or call (800) 423 -0563. Thank you. © 2009 Brooks/Cole - Cengage

3 Transition Metal Chemistry © 2009 Brooks/Cole - Cengage

4 Transition Metal Chemistry © 2009 Brooks/Cole - Cengage

5 Gems & Minerals Citrine and amethyst are quartz (Si. O 2) with a trace of cationic iron that gives rise to the color. © 2009 Brooks/Cole - Cengage

6 Gems & Minerals © 2009 Brooks/Cole - Cengage Rhodochrosite, Mn. CO 3

Reactions: Transition Metals Fe + Cl 2 Fe + O 2 © 2009 Brooks/Cole - Cengage Fe + HCl 7

Periodic Trends: Atom Radius © 2009 Brooks/Cole - Cengage 8

Periodic Trends: Density © 2009 Brooks/Cole - Cengage 9

Periodic Trends: Melting Point © 2009 Brooks/Cole - Cengage 10

Periodic Trends: Oxidation Numbers Most common © 2009 Brooks/Cole - Cengage 11

12 Metallurgy: Element Sources © 2009 Brooks/Cole - Cengage

13 Pyrometallurgy • Involves high temperature, such as Fe • C and CO used as reducing agents in a blast furnace • Fe 2 O 3 + 3 C f 2 Fe + 3 CO • Fe 2 O 3 + 3 CO f 2 Fe + 3 CO 2 • Lime added to remove impurities, chiefly Si. O 2 + Ca. O f Ca. Si. O 3 • Product is impure cast iron or pig iron © 2009 Brooks/Cole - Cengage

14 Metallurgy: Blast Furnace See Active Figure 22. 8 © 2009 Brooks/Cole - Cengage

Metallurgy: Blast Furnace Molten iron is poured from a basic oxygen furnace. © 2009 Brooks/Cole - Cengage 15

16 Metallurgy: Copper Ores Azurite, 2 Cu. CO 3·Cu(OH)2 Native copper © 2009 Brooks/Cole - Cengage

17 Metallurgy: Hydrometallurgy • Uses aqueous solutions • Add Cu. Cl 2(aq) to ore such as Cu. Fe. S 2 (chalcopyrite) Cu. Fe. S 2 (s) + 3 Cu. Cl 2 (aq) f 4 Cu. Cl(s) + Fe. Cl 2 (aq) + 2 S(s) • Dissolve Cu. Cl with xs Na. Cl Cu. Cl(s) + Cl-(aq) f [Cu. Cl 2] • Cu(I) disproportionates to Cu metal 2 [Cu. Cl 2]- f Cu(s) + Cu. Cl 2 (aq) + 2 Cl- © 2009 Brooks/Cole - Cengage

Electrolytic Refining of Cu See. Figure 22. 11 © 2009 Brooks/Cole - Cengage 18

Coordination 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. © 2009 Brooks/Cole - Cengage 19

Coordination Chemistry Pt(NH 3)2 Cl 2 “Cisplatin” - a cancer chemotherapy agent Co(H 2 O)62+ Cu(NH 3)42+ © 2009 Brooks/Cole - Cengage 20

Coordination Chemistry An iron-porphyrin, the basic unit of hemoglobin © 2009 Brooks/Cole - Cengage 21

22 Vitamin B 12 A naturally occurring cobalt-based compound Co atom © 2009 Brooks/Cole - Cengage

Nitrogenase • Biological nitrogen fixation contributes about half of total nitrogen input to global agriculture, remainder from Haber process. • To produce the H 2 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 N 2 into NH 3. • Nitrogenase consists of 2 metalloproteins: one with Fe and the other with Fe and Mo. © 2009 Brooks/Cole - Cengage 23

24 Coordination Compounds of Ni 2+ © 2009 Brooks/Cole - Cengage

Nomenclature Ni(NH 3)6]2+ A Ni 2+ ion surrounded by 6, neutral NH 3 ligands Gives coordination complex ion with 2+ charge. © 2009 Brooks/Cole - Cengage 25

26 Nomenclature Inner coordination sphere Ligand: monodentate + Cl- Ligand: bidentate Co 3+ + 2 Cl- + 2 neutral ethylenediamine molecules Cis-dichlorobis(ethylenediamine)cobalt(II) chloride © 2009 Brooks/Cole - Cengage

27 Common Bidentate Ligands Bipyridine (bipy) Acetylacetone (acac) Ethylenediamine (en) © 2009 Brooks/Cole - Cengage Oxalate (ox)

28 Acetylacetonate Complexes Commonly called the “acac” ligand. Forms complexes with all transition elements. © 2009 Brooks/Cole - Cengage

Multidentate Ligands EDTA 4 - - ethylenediaminetetraacetate ion Multidentate ligands are sometimes called CHELATING ligands © 2009 Brooks/Cole - Cengage 29

Multidentate Ligands Co 2+ complex of EDTA 4 - © 2009 Brooks/Cole - Cengage 30

31 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 [Cu. Cl 4]2 - = tetrachlorocuprate 6. Oxidation no. of metal ion indicated © 2009 Brooks/Cole - Cengage

Nomenclature [Co(H 2 O)6]2+ Hexaaquacobalt(II) H 2 O as a ligand is aqua Pt(NH 3)2 Cl 2 [Cu(NH 3)4]2+ Tetraamminecopper(II) diamminedichloroplatinum(II) NH 3 as a ligand is ammine © 2009 Brooks/Cole - Cengage 32

Nomenclature Pt( Tris(ethylenediamine)nickel(II) [Ni(NH 2 C 2 H 4 NH 2)3]2+ Ir. Cl(CO)(PPh 3)2 Vaska’s compound Carbonylchlorobis(triphenylphosphine)iridium(I) © 2009 Brooks/Cole - Cengage 33

Structures of Coordination Compounds © 2009 Brooks/Cole - Cengage 34

Isomerism • Two forms of isomerism – Constitutional – Stereoisomerism • Constitutional – Same empirical formula but different atomto-atom connections • Stereoisomerism – Same atom-to-atom connections but different arrangement in space. © 2009 Brooks/Cole - Cengage 35

36 Constitutional Isomerism Aldehydes & ketones Peyrone’s chloride: Pt(NH 3) 2 Cl 2 Magnus’s green salt: [Pt(NH 3)4][Pt. Cl 4] © 2009 Brooks/Cole - Cengage

Linkage Isomerism sunlight Such a transformation could be used as an energy storage device. © 2009 Brooks/Cole - Cengage 37

38 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. © 2009 Brooks/Cole - Cengage

39 Geometric Isomerism Cis and trans-dichlorobis(ethylenediamine)cobalt(II) chloride © 2009 Brooks/Cole - Cengage

Geometric Isomerism Fac isomer © 2009 Brooks/Cole - Cengage Mer isomer 40

41 Stereoisomerism • Enantiomers: stereoisomers that have a nonsuperimposable mirror image • Diastereoisomers: stereoisomers that do not have a non-superimposable mirror image (cistrans isomers) • Asymmetric: lacking in symmetry—will have a non-superimposable mirror image • Chiral: an asymmetric molecule © 2009 Brooks/Cole - Cengage

42 An Enantiomeric Pair [Co(NH 2 C 2 H 4 NH 2)3]2+ © 2009 Brooks/Cole - Cengage

Stereoisomerism 43 [Co(en)(NH 3)2(H 2 O)Cl]2+ These two isomers have a plane of symmetry. Not chiral. These two are asymmetric. Have non -superimposable mirror images. © 2009 Brooks/Cole - Cengage

44 Stereoisomerism These are non-superimposable mirror images [Co(en)(NH 3)2(H 2 O)Cl]2+ © 2009 Brooks/Cole - Cengage

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 f ligand field theory © 2009 Brooks/Cole - Cengage 45

Bonding 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 © 2009 Brooks/Cole - Cengage 46

Bonding in Coordination Compounds © 2009 Brooks/Cole - Cengage 47

Crystal Field Theory • Consider what happens as 6 ligands approach an Fe 3+ 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. , H 2 O > Cl© 2009 Brooks/Cole - Cengage 48

Octahedral Ligand Field © 2009 Brooks/Cole - Cengage 49

Tetrahedral & Square Planar Ligand Field © 2009 Brooks/Cole - Cengage 50

Crystal 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 © 2009 Brooks/Cole - Cengage 51

52 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 on size of ∆o and P, the pairing energy. • P = energy required to create e- pair. © 2009 Brooks/Cole - Cengage

Magnetic Properties/Fe 2+ • High spin Paramagnetic • Weak ligand field strength and/or lower Mn+ charge • Higher P possible? • Low spin Diamagnetic © 2009 Brooks/Cole - Cengage • Stronger ligand field strength and/or higher Mn+ charge • Lower P possible? 53

High and Low Spin Octahedral Complexes See Figure 22. 25 High or low spin octahedral complexes only possible for d 4, d 5, d 6, and d 7 configurations. © 2009 Brooks/Cole - Cengage 54

Crystal Field Theory Why are complexes colored? Fe 3+ © 2009 Brooks/Cole - Cengage Co 2+ Ni 2+ Cu 2+ Zn 2+ 55

56 Crystal Field Theory Why are complexes colored? – © 2009 Brooks/Cole - Cengage Note that color observed for Ni 2+ in water is transmitted light

Crystal Field Theory • Why are complexes colored? – Note that color observed is transmitted light Absorption band © 2009 Brooks/Cole - Cengage 57

Crystal 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 – d 1, d 4, d 6, and d 9 --> 1 absorption band – d 2, d 3, d 7, and d 8 --> 3 absorption bands • Spectrochemical series — ligand dependence of light absorbed. © 2009 Brooks/Cole - Cengage 58

59 Light Absorption by Octahedral Co 3+ Complex Ground state Excited state Usually excited complex returns to ground state by losing energy, which is observed as heat. © 2009 Brooks/Cole - Cengage

Spectrochemical Series • d orbital splitting (value of ∆o) is in the order I- < Cl- < F- < H 2 O < NH 3 < en < phen < CN- < CO As ∆ increases, the absorbed light tends to blue, and so the transmitted light tends to red. © 2009 Brooks/Cole - Cengage 60

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 Fe 4+ – When amethyst is heated, it forms citrine as Fe 4+ is reduced to Fe 3+ © 2009 Brooks/Cole - Cengage 61 Prussian blue contains Fe 3+ and Fe 2+