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Chapter 24 Transition Metals & Coordination Compounds

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

2 Transition Metals contain e- in d Orbitals
Breath – slow down!

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.

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 Slow down - Breath

7 Electron Configuration
[Kr] 5s2 4d2

8 Atomic Size Decreasing Size Increas Ing S i ze

9 Atomic Size Keep it simple! breath 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

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

13 Electronegativity Au: EN = 2.4 Compared to P: EN = 2.1 !! Gold breath slow down 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 Scandium 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 2:30 pm) David N. Blauch -

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 Coordination Number 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 L : M Lewis Acid Lewis Base 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

20 Geometries Anne Marie Helmenstine, Ph.D., Guide

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 Isomers Structural Isomers Stereoisomers
Coordination Isomers Linkage Isomers Stereoisomers Geometric Isomers cis-trans fac-mer Optical Isomers 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 Isomers Coordination Isomers
pentaamminesulfatochromium(III) bromide pentaamminebromochromium(III) sulfate David N. Blauch -

24 Structural Isomers Linkage Isomers
pentaamminenitrocobalt(III) ion pentaamminenitritocobalt(III) ion David N. Blauch -

25 Stereoisomers Geometric Isomers: cis-trans
cis-diamminedichloroplatinum(II) trans-diamminedichloroplatinum(II) David N. Blauch -

26 Stereoisomers Geometric Isomers: fac-mer
fac-triamminetrichlorocobalt(III) mer-triamminetrichlorocobalt(III) David N. Blauch -

27 Stereoisomers Optical Isomers
Mirror Images Non-superimposable Enantimomers Chiral: optically active (rotates polarized light)

28 Chirality Determining Optical Activity
fac mer David N. Blauch -

29 Chirality Determining Optical Activity
Superimposable - No optical activity

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