Formation of Complex Compounds
1. Definition and Characteristics of Complex Compounds
Complex compounds, also known as coordination compounds, consist of a central metal atom or ion
surrounded by molecules or ions called ligands. These compounds exhibit unique properties such
as variable oxidation states, distinct colors, and catalytic activity.
2. Coordination Number and Geometry
The coordination number refers to the number of ligand donor atoms directly bonded to the central
metal ion. Common coordination numbers and their geometries include:
- 2 (Linear) - Example: [Ag(NH3)2]+
- 4 (Tetrahedral or Square Planar) - Example: [Ni(CN)4]2-
- 6 (Octahedral) - Example: [Fe(CN)6]3-
3. Types of Ligands and Chelation
Ligands are classified based on the number of donor atoms:
- Monodentate: Bind through a single donor atom (e.g., NH3, Cl-)
- Bidentate: Bind through two donor atoms (e.g., ethylenediamine)
- Polydentate: Bind through multiple donor atoms (e.g., EDTA)
Chelation occurs when a polydentate ligand forms a ring with the metal ion, increasing stability.
4. The Role of d-Orbitals in Complex Formation
Transition metal complexes involve d-orbitals in bonding. Ligands donate electron pairs, which
interact with the metal's d-orbitals, forming coordinate covalent bonds. This interaction influences
the geometry and stability of the complex.
5. Crystal Field Theory and Stability
Crystal Field Theory (CFT) explains the splitting of d-orbitals in a ligand field:
- In an octahedral field, d-orbitals split into t2g (lower energy) and eg (higher energy) orbitals.
- Strong field ligands cause greater splitting, leading to low-spin complexes.
- Weak field ligands cause smaller splitting, leading to high-spin complexes.
The stability of a complex depends on factors like ligand strength and metal ion charge.
6. Applications of Complex Compounds
Complex compounds have numerous applications:
- Medicine: Cisplatin (anticancer drug)
1. Definition and Characteristics of Complex Compounds
Complex compounds, also known as coordination compounds, consist of a central metal atom or ion
surrounded by molecules or ions called ligands. These compounds exhibit unique properties such
as variable oxidation states, distinct colors, and catalytic activity.
2. Coordination Number and Geometry
The coordination number refers to the number of ligand donor atoms directly bonded to the central
metal ion. Common coordination numbers and their geometries include:
- 2 (Linear) - Example: [Ag(NH3)2]+
- 4 (Tetrahedral or Square Planar) - Example: [Ni(CN)4]2-
- 6 (Octahedral) - Example: [Fe(CN)6]3-
3. Types of Ligands and Chelation
Ligands are classified based on the number of donor atoms:
- Monodentate: Bind through a single donor atom (e.g., NH3, Cl-)
- Bidentate: Bind through two donor atoms (e.g., ethylenediamine)
- Polydentate: Bind through multiple donor atoms (e.g., EDTA)
Chelation occurs when a polydentate ligand forms a ring with the metal ion, increasing stability.
4. The Role of d-Orbitals in Complex Formation
Transition metal complexes involve d-orbitals in bonding. Ligands donate electron pairs, which
interact with the metal's d-orbitals, forming coordinate covalent bonds. This interaction influences
the geometry and stability of the complex.
5. Crystal Field Theory and Stability
Crystal Field Theory (CFT) explains the splitting of d-orbitals in a ligand field:
- In an octahedral field, d-orbitals split into t2g (lower energy) and eg (higher energy) orbitals.
- Strong field ligands cause greater splitting, leading to low-spin complexes.
- Weak field ligands cause smaller splitting, leading to high-spin complexes.
The stability of a complex depends on factors like ligand strength and metal ion charge.
6. Applications of Complex Compounds
Complex compounds have numerous applications:
- Medicine: Cisplatin (anticancer drug)
