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Chapter 24 Transition Metals & Coordination Compounds 24.2 Properties of Transition Metals o Review Electron Configuration o Trends in the Periodic Table 24.3 Coordination Compounds o The Basics o Example of Naming 24.4 Structure and Isomerization Slide 2 Transition Metals contain e - in d Orbitals 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 Slide 3 Why Are Transition Metals & Coordination Compounds Important? Therapeutic drugs Chemical Sensors Coloring agents o Paints o Cosmetics Biological Molecules o Hemeglobin o Chlorophyll Gems (Jewelry & Technological Applications) o Rubies, Emeralds, Garnets, etc. o Lasers Slide 4 24.2 Properties of Transition Metals Moderate to High Densities Good Electrical Conductivity High Melting Points Moderate to Extreme Hardness http://www.tutorvista.com/chemistry/shapes-of-d-orbitals 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. Slide 5 Electron Configuration Increasing EnergyIncreasing Energy (n-1)d (n-2)f Slide 6 Electron Configuration [noble gas] n s 2 (n- 1 ) d x [noble gas] n s 2 (n- 2 ) f 14 (n- 1 ) d x Slide 7 Electron Configuration [Kr]5s 2 4d 2 http://malaxoschemistry.wikispaces.com/Periodic+Table Slide 8 Atomic Size Decreasing Size IncreasIngSizeIncreasIngSize http://malaxoschemistry.wikispaces.com/Periodic+Table Slide 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. Slide 10 Ionization Energy Increases DecreasesDecreases http://malaxoschemistry.wikispaces.com/Periodic+Table Slide 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. Slide 12 Electronegativity http://malaxoschemistry.wikispaces.com/Periodic+Table Increases DecreasesDecreases Slide 13 Electronegativity Exception to the trend: There is an increase in electronegativity from the 3d (1 st row transition metals) to the 4d (2 nd row transition metals). Au: EN = 2.4 Compared to P: EN = 2.1 !! Slide 14 Oxidation States In general, stability is found in full or half- full shells, and in a configuration that looks like a noble gas. Slide 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 David N. Blauch - http://www.chm.davidson.edu/vce/index.htm *Corrected 4/15/11 @ 2:30 pm) Slide 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 o Primary Valence Oxidation State of the central metal o Secondary Valence Number of molecules or ions directly attached to the central metal or Coordination Number Example: [Co(NH 3 ) 6 ]Cl 3 o The Primary Valence or Oxidation State of Co is +3 o The Secondary Valence or Coordination Number is 6 (6 ammonia ligands are directly attached to Co Other cobalt(III) coordination compounds [Co(NH 3 ) 6 ]Cl 3 [Co(NH 3 ) 5 Cl]Cl 2 [Co(NH 3 ) 4 Cl 2 ]Cl Slide 17 Coordinate Covalent Bonds Lewis Acid-Base Adduct the ligand donates its electrons to the empty metal orbitals to form a coordinate covalent bond Lewis Acid Lewis Base M L : Adduct Slide 18 Some Common Ligands Slide 19 Chelating Agents Ligands can have one or more bonding pairs of electrons o Monodentate o Bidentate or Polydentate Complex ions with bidentate or polydentate ligands are chelates, and the coordinating ligands are chelating agents EDTA is hexadentate http://library.kiwix.org:4201/A/Inorganic_chemistry.htm Co Slide 20 Geometries Anne Marie Helmenstine, Ph.D.Anne Marie Helmenstine, Ph.D., About.com Guide Slide 21 Naming Coordination Compounds [Mn(CO)(NH 3 ) 5 ]SO 4 (neutral ligands are written before charged ligands in the formula) Cation 1st o Name the ligands in alphabetical order ammine carbonyl o Add a prefix to indicate the number of ligands pentaammine o Name the metal ion Manganese(II) Anion 2 nd o Sulfate Pentaamminecarbonylmanganese(II) sulfate Slide 22 24.4 Structure & Isomerism Isomers Structural Isomers Coordination IsomersLinkage Isomers Stereoisomers Geometric Isomers cis-trans fac-mer Optical Isomers Same formula different structures Different connectivities Same connectivities different spacial arrangements Ligands & counter ions trade places Ligands coordinate in different ways Different spacial arrangements Mirror images Slide 23 Structural Isomers Coordination Isomers David N. Blauch - http://www.chm.davidson.edu/vce/index.htm pentaamminesulfatochromium(III) bromide pentaamminebromochromium(III) sulfate Slide 24 Structural Isomers Linkage Isomers David N. Blauch - http://www.chm.davidson.edu/vce/index.htm pentaamminenitrocobalt(III) ionpentaamminenitritocobalt(III) ion Slide 25 Stereoisomers Geometric Isomers: cis-trans cistrans David N. Blauch - http://www.chm.davidson.edu/vce/index.htm cis-diamminedichloroplatinum(II)trans-diamminedichloroplatinum(II) Slide 26 Stereoisomers Geometric Isomers: fac-mer facmer David N. Blauch - http://www.chm.davidson.edu/vce/index.htm fac-triamminetrichlorocobalt(III)mer-triamminetrichlorocobalt(III) Slide 27 Stereoisomers Optical Isomers Mirror Images Non-superimposable Enantimomers Chiral: optically active (rotates polarized light) http://www.wikidoc.org/inde x.php/Chirality_%28chemist ry%29 http://en.wikipedia.org/wiki/Chirality_%28 electromagnetism%29 Slide 28 Chirality Determining Optical Activity fac mer David N. Blauch - http://www.chm.davidson.edu/vce/index.htm Slide 29 Chirality Determining Optical Activity Superimposable - No optical activity