Chapter 24 Transition Metals & Coordination Compounds

1. Chapter 24Transition Metals &Coordination Compounds • 24.2 Properties of Transition Metals • Review Electron Configuration • Trends in the Periodic Table • 24.3 Coordination Compounds • The Basics • Example of Naming • 24.4 Structure and Isomerization

2. Transition Metals contain e- in d Orbitals http://www.can-do.com/uci/lessons98/Periodic.html http://www.can-do.com/uci/lessons98/Periodic.html

3. Why Are Transition Metals & Coordination Compounds Important? • Therapeutic drugs • Chemical Sensors • Coloring agents • Paints • Cosmetics • Biological Molecules • Hemeglobin • Chlorophyll • Gems (Jewelry & Technological Applications) • Rubies, Emeralds, Garnets, etc. • Lasers

4. 24.2 Properties of Transition Metals • Moderate to High Densities • Good Electrical Conductivity • High Melting Points • Moderate to Extreme Hardness Due to the delocalization of d electrons in metallic bonding Exceptions: Elements with filled d orbitals, which prevents d-d bonding. Hg has a low melting point and is liquid at room temperature. http://www.tutorvista.com/chemistry/shapes-of-d-orbitals

5. Electron Configuration Increasing Energy (n-1)d (n-2)f

6. Electron Configuration [noble gas] ns2 (n-1)dx [noble gas] ns2 (n-2)f14 (n-1)dx

7. Electron Configuration [Kr] 5s2 4d2 http://malaxoschemistry.wikispaces.com/Periodic+Table

8. Atomic Size Decreasing Size Increas Ing S i ze http://malaxoschemistry.wikispaces.com/Periodic+Table

9. Atomic Size Exception to the trend: Electrons in the f-orbitals are not effective at shielding outer shell electrons from nuclear charge. So, the outer electrons are held in close – this is known as lanthanide contraction.

10. Ionization Energy Increases Decreases http://malaxoschemistry.wikispaces.com/Periodic+Table

11. Ionization Energy Exception to the trend: Note that 5d elements have a greater ionization energy. This is again due to outer shell electron being held closer to the nucleus, so it take more energy to pull them away.

12. Electronegativity Increases Decreases http://malaxoschemistry.wikispaces.com/Periodic+Table

13. Electronegativity Au: EN = 2.4 Compared to P: EN = 2.1 !! Exception to the trend: There is an increase in electronegativity from the 3d (1st row transition metals) to the 4d (2nd row transition metals).

14. Oxidation States In general, stability is found in full or half-full shells, and in a configuration that looks like a noble gas.

15. 24.3 Coordination Compounds • Complex Ion - Central Metal bound to one or more ligands • Ligands are Lewis Base* (electron donors) and can be either neutral or negatively charged • The charge on the complex ion is balance by counter ions of opposite charge The combination of a complex ion and counter ions results in a coordination compound *Corrected 4/15/11 @ 2:30 pm) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

16. A Little Background • In 1893, Swiss chemist Alfred Werner came up with the idea that a central metal could have 2 types of interactions • Primary Valence – Oxidation State of the central metal • Secondary Valence – Number of molecules or ions directly attached to the central metal or CoordinationNumber • Example: [Co(NH3)6]Cl3 • The Primary Valence or Oxidation State of Co is +3 • The Secondary Valence or Coordination Number is 6 (6 ammonia ligands are directly attached to Co • Other cobalt(III) coordination compounds • [Co(NH3)6]Cl3 • [Co(NH3)5Cl]Cl2 • [Co(NH3)4Cl2]Cl

17. Coordinate Covalent Bonds • Lewis Acid-Base Adduct – the ligand donates it’s electrons to the empty metal orbitals to form a coordinate covalent bond M : L Lewis Base Lewis Acid Adduct

18. Some Common Ligands

19. Chelating Agents • Ligands can have one or more bonding pairs of electrons • Monodentate • Bidentate or Polydentate • Complex ions with bidentate or polydentate ligands are chelates, and the coordinating ligands are chelating agents Co EDTA is hexadentate http://library.kiwix.org:4201/A/Inorganic_chemistry.htm

20. Geometries Anne Marie Helmenstine, Ph.D., About.comGuide

21. Naming Coordination Compounds • [Mn(CO)(NH3)5]SO4 (neutral ligands are written before charged ligands in the formula) • Cation 1st • Name the ligands in alphabetical order • ammine • carbonyl • Add a prefix to indicate the number of ligands • pentaammine • Name the metal ion • Manganese(II) • Anion 2nd • Sulfate • Pentaamminecarbonylmanganese(II) sulfate

22. 24.4 Structure & Isomerism Same formula – different structures Same connectivities –different spacial arrangements Different connectivities Ligands & counter ions trade places Ligands coordinate in different ways Different spacial arrangements Mirror images

23. Structural IsomersCoordination Isomers pentaamminesulfatochromium(III) bromide pentaamminebromochromium(III) sulfate David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

24. Structural IsomersLinkage Isomers pentaamminenitrocobalt(III) ion pentaamminenitritocobalt(III) ion David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

25. StereoisomersGeometric Isomers: cis-trans cis trans cis-diamminedichloroplatinum(II) trans-diamminedichloroplatinum(II) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

26. StereoisomersGeometric Isomers: fac-mer fac mer fac-triamminetrichlorocobalt(III) mer-triamminetrichlorocobalt(III) David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

27. StereoisomersOptical Isomers • Mirror Images • Non-superimposable • Enantimomers • Chiral: optically active (rotates polarized light) http://www.wikidoc.org/index.php/Chirality_%28chemistry%29 http://en.wikipedia.org/wiki/Chirality_%28electromagnetism%29

28. ChiralityDetermining Optical Activity fac mer David N. Blauch - http://www.chm.davidson.edu/vce/index.htm

29. ChiralityDetermining Optical Activity Superimposable - No optical activity