Coordination Compounds

• Coordination Complexes


  The product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coordinate covalent bonds

  
• Categories of elements in the periodic table

  • Main group metals
  • Transition metals
  • Lanthanides
  • Actinides

  
• Only need to know Sc to Zn, by heart, for this course
• Lanthanoids and Actinoids


  1. block elements but not transition metals
• Transition vs Main Group Metals

  • Look like metals
  • Malleable and ductile
  • Conduct heat and electricity
  • Form positive ions

  
• Transition Metals


  • Have an incomplete d-subshell of electrons, or which gives rise to a cation with an incomplete d-subshell
  • The terms 'd-block metal' and 'transition metal' are not interchangeable

  
• General Properties of Transition Metals

  • They are all metals
  • They are almost all hard, strong, high-melting, high-boiling metals that conduct heat and electricity well
  • With very few exceptions, they exhibit variable valence, and their ions and compounds are coloured in one if not all oxidation states
  • Because of partially filled shells, they form at least some paramagnetic compounds
• Transition Metal Chemistry


  • Differences in electronic configurations from expected progressive filling of 3d, 4d, and 5d atomic orbitals
  • Half filled d and s orbitals maximizes stability and exchange energy

  
• Properties of Transition Metals

  • Usually have several oxidation states
  • Ions are usually coloured
  • Form many coordination compounds
  • Involved in redox reactions
  • Varying degrees of electropositive character
• Coordination Compound


  The product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coordinate covalent bonds

  
• Ligand


  Lewis bases that contain at least one pair of electrons to donate to a metal atom/ion
• Coordination Sphere


  Consists of the central metal atom/ion plus its attached ligands

  
• Coordination Number (CN)


  The number of donor atoms bonded to the central metal atom/ion

  
• Coordinate Covalent Bond


  A covalent bond in which one atom (the donor atom) supplies both electrons
• Monodentate Ligands


  • F-
  • Br-
  • H2O
  • OH-
  • CN-
  • Cl-
  • I-
  • NH3
  • CO
  • SCN-
• [RhI2(CO)2]-


  • Used as a catalyst in the "Monsanto Process" for making acetic acid
• [Cu(NH3)4]2+


  • Present in some brands of waterbed conditioners, responsible for inhibiting the growth of fungi and bacteria
• Bidentate Ligands


  Lewis bases that donate two pairs of electrons to a metal atom
• Polydentate ligands form more stable compounds than monodentate ones
• Ethylenediamminetetraacetate ion (EDTA4-)


  • [Fe(EDTA)]2-
• IF7


  • Coordination number = 7, Pentagonal bipyramidal structure
• [HgCl3]-


  • Coordination number = 3, Trigonal planar structure
• Fe(CO)5


  • Coordination number = 5, Trigonal bipyramidal structure

  
• [Ni(CN)5]2-


  • Coordination number = 5, Square pyramidal structure
• Aqueous Metal Ions


  Transition metal cations in aqueous solution are usually symbolized as Mn+ (aq)

  
• (C2O4)3]3-


  Complex ion containing the bidentate oxalate ion
• Complex ion


  • Water-soluble
  • Can be washed away
• Coordination complex


  • 6 bonds
  • 4 ligands
• Coordination complex


  • 6 bonds
  • 3 bidentate ligands
• [Fe(EDTA)]2-


  Coordination complex with polydentate EDTA ligand
• IF7


  Coordination number 7, pentagonal bipyramidal structure

  
• [HgCl3]-


  Coordination number 3, trigonal planar structure
• Fe(CO)5


  Coordination number 5, trigonal bipyramidal structure

  
• The most common coordination numbers for coordination compounds are 2, 4 and 6
• [Ni(CN)5]2-


  Coordination number 5, square pyramidal structure
• Mn+ (aq)


  Aqueous metal ion, with metal symbol and charge
• [Fe(OH2)6]3+


  Octahedral aqueous metal ion complex

  
• The element directly bonded to the metal center is written first in coordination compounds

  
• Heme


  Biological molecule with iron center
• Vitamin B12


  Biological molecule with cobalt center in octahedral shape