Introduction to Coordination Chemistry

Overview

• Presenter: Chad from Chad's Prep.
• Topics: Science prep for high school, college, MCAT, DAT, and OAT.
• Focus: Introduction to coordination chemistry and coordinate covalent bonds.

Coordinate Covalent Bonds

• Covalent Bonds: Sharing of electrons between non-metals.
• Coordinate Covalent Bonds:
  • One atom donates both electrons, while the other does not share any.
  • Involves Lewis acids (accept electron pairs) and Lewis bases (donate electron pairs).

Metal Ions and Ligands

• Central Metal Ion: Usually a metal ion acting as a Lewis acid.
• Ligands: Molecules (neutral or anions) that donate a lone pair of electrons. Named as ligands.
  • Common Ligands: Ammonia and water (neutral ligands), anions.

Geometries and Coordination Numbers

• Linear: 2 bonds, 180 degrees apart.
• Square Planar: 4 bonds, 90 degrees apart in a single plane.
• Tetrahedral: 4 bonds, 109.5 degrees apart in a 3D structure.
• Octahedral: 6 bonds, 90 degrees or 180 degrees apart.
• Coordination Number: Number of bonds to the central metal ion.

Coordination Sphere

• Definition: Includes the central metal ion and its bonded ligands.
• Complex Ions:
  • Complex Cation: Overall positive charge.
  • Complex Anion: Overall negative charge.
  • Neutral Complex: No charge.
• Importance: Components inside coordination spheres may not participate in chemical reactions.

Example Problem

• Formula: Central metal ion listed first, followed by ligands, and then counter ions.
• Reaction with AgNO3: Only free counter ions outside the coordination sphere react.

Polydentate Ligands

• Definition: Ligands that can form more than one bond with the central metal ion.
• Examples: Ethylenediamine (bidentate), diethylenetriamine (tridentate), EDTA (hexadentate).
• Chelating Agents:
  • Bind and sequester metal ions.
  • Used in medicine for heavy metal poisoning and in biochemical reactions.

Naming Ligands

• Naming: Specific names used for ligands in complex ions.
• Key Names:
  • Water: Aqua
  • Ammonia: Amine

Conclusion

• Importance of understanding coordination chemistry for exams.
• Resources for further practice available through Chad's Prep.