Chemistry Coordination Compounds

Introduction

• Coordination Compounds: These are complex molecules. Their characteristic is that they have a central metal atom that is bound with either neutral molecules or anions.
• In coordination, sharing of electrons occurs.

Importance of Coordination Compounds

• Biological Systems: Chlorophyll (of magnesium), Hemoglobin (of iron), Vitamin B12 (of cobalt)
• Industrial Applications: Catalyst, Medicinal Chemistry, Textile Dyeing

Theories

• Werner's Theory: Concept of Primary and Secondary valency
• Valence Bond Theory
• Crystal Field Theory

Werner's Theory

• Primary Valency: Oxidation number; Ionizable
• Secondary Valency: Coordination number; Non-ionizable
• Coordination Polyhedra: Specific spatial arrangement

Coordination Entity and Ligands

• Central Metal Atom or Ion
• Ligands: Ions or Molecules linked to the central atom
• Dentisity: Number of donor atoms in ligands
  • Monodentate (Unidentate): One donor atom (like Cl⁻, NH₃)
  • Bidentate: Two donor atoms (like the oxalate ion)
  • Polydentate: More donor atoms (like EDTA)

Nomenclature of Coordination Compounds

• Cation first, Anion later
• Ligands' name first, Central metal later
• Anionic ligands' names end with 'o'
• Prefixes for multiple ligands (di, tri, etc.)
• Oxidation state in Roman numerals for Central Atom

Valence Bond Theory

• Hybridization: SP, d₂sp₃, etc.
• Geometry: Tetrahedral, Octahedral, etc.
• Magnetic Behavior: Based on unpaired electrons

Crystal Field Theory

• Splitting of D Orbitals: In the presence of ligands
• Strong and Weak Ligands: Based on the amount of splitting
• Color: Due to D-D electron transition

Limitations of Theories

• Valence Bond Theory: No quantitative interpretation of magnetic data
• Crystal Field Theory: Does not consider covalent character

Utility

• Biological Systems: Chlorophyll, Hemoglobin
• Industries: Catalysts, Medicinal applications

Conclusion

• The study of coordination compounds is essential as they play a significant role in life and industries.