Lecture Notes: Coordination Compounds

Introduction to Coordination Compounds

• Coordination compounds are a new chapter in inorganic chemistry.
• Completion of D and F block chapters is expected prior to this lecture.
• Importance of taking notes and watching lectures completely.

Types of Addition Compounds

• Addition Compounds: Formed by fusing two salts.
  • Double Salt: Formed by fusing two salts in equal molar ratio.
  • Complex Salt: Formed by fusing two salts in unequal molar ratio.

Characteristics of Double and Complex Salts

• Double Salt:

  • Fully dissociates in solution.
  • Example: Carnalite (KCl·MgCl2·6H2O).

• Complex Salt:

  • Does not fully dissociate; retains some structure.
  • Example: Copper(II) sulfate with ammonia (Cu(NH3)4SO4).

Important Terminologies in Coordination Compounds

1. Coordination Compound: Formed by a central metal atom/ion and ligands.
2. Ligand: An ion or molecule that donates a pair of electrons to the central atom.
3. Coordination Sphere: The entire structure of the coordination compound, including the central metal and ligands, usually enclosed in square brackets.
4. Counter Ions: Ions present outside the coordination sphere.
5. Coordination Number: Number of ligand donor atoms bonded to the central metal atom.
6. Coordination Polyhedron: The shape formed by ligands surrounding the central metal atom.

Types of Ligands

• Based on Charge:

  • Negatively Charged Ligands: Examples - F-, OH-, Br-. Naming: Ends in '-ido'.
  • Positively Charged Ligands: Examples - NO2+, NH3+. Naming: Ends in '-ium'.
  • Neutral Ligands: Examples - H2O (aqua), NH3 (ammine), CO (carbonyl).

• Based on Denticity:

  • Monodentate: One donor site (e.g., F-, OH-).
  • Bidentate: Two donor sites (e.g., Ethylenediamine).
  • Polydentate: Multiple donor sites, e.g., EDTA (Hexadentate).

Stability and Chelation

• Chelation: Formation of a chelate ring during complex formation.
• The greater the number of chelate rings, the more stable the complex.

Key Concepts

• Ligands are either neutral, positively, or negatively charged ions.
• Understanding ligands is essential for mastering coordination compounds.
• The structure and bonding of coordination compounds depend on the geometry of the arrangement of ligands.

Conclusion

• Coordination compounds are an important and interesting topic with logical reasoning behind memorization.
• Ensure understanding of definitions and classifications discussed in the lecture.