Coordination Compounds

1
Coordination Compounds
Almost all metal ions found as complexes
Complex Ion
Ligand
Metal Ion (Co3)
Counter Ion, for charge balance
2
Ligands

• Ligand a lewis base that binds to a metal ion
• Remember
• Lewis Acid electron-pair acceptor
• Lewis Base electron-pair donor (has lone pair)
• Ligand binding results in a coordinate covalent
  bond

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Some Common Ligands

• Monodentate (one bond to metal ion)

19
4
Some Common Ligands

• Bidentate Ligands (two bonds to metal ion)
• Any ligand with more than one bond called a
  chelating ligand

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Some Common Ligands

• Polydentate Ligands
• Tridentate (3 bonds)
• Tetradentate (4 bonds)
• EDTA (ethylene diamine tetra acetate)

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Pay attention to

• what part is the complex ion, what is the counter
  ion ?
• charge of the complex ion ?
• oxidation state of transition metal ?
• are ligands charged or neutral ?

Complex Ion
Transition Metal Coordination Compound
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Determining Charge of Compound

• Necessary for Naming
• Ligands
• Some negatively charged
• Some neutral
• Metal Ion
• Always positively charged!
• Counter Ions
• Positive or Negative to balance complex ion

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Complex Ion
If Mn is 2

• Complex Ion Charge
• Mn(H2O)6
• Mn(H2O)5Cl
• Mn(H2O)4Cl2
• MnCl6

• 2
• 1
• 0
• 4

• Ligands
• H2O
• NH3
• Cl
• OH

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Transiton Metal Coordination Compound

• If Mn is 2

• Compound
• Mn(H2O)6
• Mn(H2O)5Cl
• Mn(H2O)4Cl2
• MnCl6

Cl2 Cl
K4
10
Charges on Vanadium?

• V (NH3)6 Cl3
• V (H2O)4 (OH)2 Cl3
• K3 V Cl6
• K V Cl3 (NH3)3

3 5 3 2

• Ligands
• H2O
• NH3
• Cl
• OH

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Naming t.m. coordination compound
Co(NH3)5ClCl2 penta amine chloro cobalt(III)
chloride K3Fe(CN)6 potassium hexacyanoferrate
(III)

• cation is named before anion
• ligands are named before metal ion
• in naming ligands, an o is added to the root name
  of an anion (e.g. fluoro, bromo). For a neutral
  ligand, the name of the molecule is used, with
  exception of H2O, NH3, CO and NO.
• mono, di, tri, tetra, penta and hexa are used to
  denote the no. of simple ligands.
• bis, tris, tetrakis are used for more complicated
  ligands.
• oxidation state of central metal ion by a roman
  number.
• for gt1 type of ligand, ligands named in
  alphabetical order
• if the complex ion has negative charge, -ate
  (suffiz) is added to the name of the metal.

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Nomenclature

• Complex Ions ( prefix ligand )repeat
  metal (charge)

Multiple Ligands Order alphabetically (by
ligand, not prefix)
Exceptions
Examples Mn Br6 1 V (H2O)4 (OH)2 3
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Nomenclature

• Complex Ions ( prefix ligand )repeat
  metal (charge)

Example Fe (NH3)6 3
Examples Pt Cl4 2 Fe Cl6 3
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Complete Names

• cation anion
• simple anions add ide (e.g. chloride)
• or use name of polyatomic ion
• Examples
• Fe (NH3)6 Cl3
• Mn Br6 NO3
• Ca Pt Cl4

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Bidentate Ligands

• Name as you would monodentate ligands
• Except, different prefixes
• (none)
• bis
• tris
• tetrakis
• Examples
• Co(en)(H2O)4Cl2
• Co(en)2(H2O)2Cl2