Metal Complexes

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Metal Complexes

• With your Chemistry 1B Host
• Dr. Mike Daniel

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Metal Complexes

• Coordinate Covalent Bonds - A bond where one atom
  donates both e-
• Lewis Acid - Substance that accepts pair of e-
• Lewis Base - Substance that donates pair of e-
• H O-H ? H2O

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Metal Complexes

• Lewis Acid - Substance that accepts pair of e-
• Lewis Base - Substance that donates pair of e-
• Mn OH2 ? M-OH2

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Metal Complexes

• Metal acts as Lewis Acid, accepting e- pairs
• e- pair donor, is a Lewis Base, called a Ligand

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Ligand

• Ligand
• Monodentate (literally, one tooth) Ligand, a
  ligand that forms one coordinate covalent bond
  using 1 atom and 1 e- pair
• Examples
• Halides
• H2O, NH3, CN-,

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Ligand

• Bidentate Ligand - Have two donor atoms
• Examples
• C2O4-2 Oxalate ion
• NH2CH2CH2NH2, ethylenediamine (en)
• Polydentate Ligand - Having more than one donor
  atom
• Polydentate Ligands that form rings called
  Chelates or Chelating Agent

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Ligand

• Bidentate Ligand - Have two donor atoms
• Examples are also chelates

Oxalate Ion
en
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Metal Complex Formulas

• Metal Ligand
• Pt (NH3)4 Cl2 Br2
• What is charge on Pt?
• Cr (H2O)4 Cl2 Cl
• What is charge on Cr?
• K2 Pt Cl6 Pt Charge?

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Chelate Effect

• Complexes with chelates are more stable than with
  monodentate ligands.
• Monodentate Ligand can leave if bond breaks.
• Polydentate Ligand, if one bond breaks, another
  bond holds it near metal so the donor atom can
  reform bond

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Chelate Effect
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Coordination Number and Structure

• Coordination number donor atoms attached
  bonds to Metal

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Coordination Number and Structure
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Isomers

• Isomers are compounds with same formulas but
  different structures (and different properties)
• Cr (NH3)5 SO4 Br vs. Cr (NH3)5 Br SO4
• 1st Cmp AgNO3 (aq) -gt ppt
• 1st Cmp Ba(NO3)2 (aq) -gt NAR

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Isomers

• Cr (NH3)5 SO4 Br vs. Cr (NH3)5 Br SO4
• 2nd Cmp AgNO3 (aq) -gt NAR
• 2nd Cmp Ba(NO3)2 (aq) -gt ppt

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Stereoisomers

• Isomers that arise as a result of various
  possible orientation of atoms in space
• Geometric Isomers are Stereoisomers with
  different geometries
• Cis Isomer has two groups on same side of
  molecule
• Trans Isomer has two groups on different sides of
  molecule

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Cis and Trans Pt (NH3)2 Cl2
Cis Active against Testicular, Ovarian, Bone
cancer
Trans Inactive
Return to Uses
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Cis and Trans Co (NH3)4 Cl2
Trans Green Cis - Violet
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Optical Isomers

• Stereoisomers that are mirror images of each
  other but are not superimposable
• Superimposable means one structure and its mirror
  image could blend perfectly with every part of
  one coinciding with other.
• E.G. Your right and left hand are mirror images
  of each other but are not superimposable, (your
  right hand doesnt fit into a left glove)

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Optical IsomersCo(en)2NH3Cl
Mirror Plane
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Optical Isomers

• Optical Isomers have identical properties except
• They rotate polarized light in different
  directions
• They will react differently with another
  optically active substance

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Optical Isomers

• Optical Isomers more important in organic
  chemistry
• Tetrahedron with 4 different attached groups will
  be optically active.

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Uses of Metal Complexes

• Photosynthesis Mg2 porphyrin convert light
  energy, CO2, water and minerals into
  carbohydrates, and other compounds
• Green Color due to Chlorophyll absorbing red and
  purple light

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Chlorophyll
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Uses of Metal Complexes

• Hemoglobin Fe2 porphyrin transports O2

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Hemoglobin
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Uses of Metal Complexes

• Color Dyes Cu2 phthalocyanine blue used for
  inks, paint, blue jeans
• Removal of Metals
• Water Softening (removal of Ca2, Mg2, Fe2)
• Poison Treatment (removal of Hg2 Pb2)

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Uses of Metal Complexes

• Cancer Treatment
• Soil Treatment Control of plant uptake of
  metals, Fe (en)3 3 provides iron to oaks
• Electroplating Metal Complexes provide more
  uniform, better looking and adherent surface.