Chapter Notes: Coordination Compounds (Class 12)
1. Introduction
Coordination compounds are compounds wherein a vital metallic atom/ion is bonded to a
number of ions or impartial molecules (referred to as ligands).
These compounds are critical in organic structures (e.G. Hemoglobin, nutrition B12, chlorophyll)
and in industry (e.G. Catalysts, electroplating).
2. Important Terms
Coordination Entity: Central metallic ion + ligands connected.
Example: [Co(NH3)6]Cl3
Central Metal Atom/Ion: Lewis acid (accepts electron pair). Usually transition metals.
Ligands: Molecules/ions donating a couple of electrons to the vital atom.
Monodentate (donates through one atom): Cl–, H2O, NH3
Bidentate: en (ethane-1,2-diamine), C2O4²– (oxalate)
Polydentate: EDTA⁴– (hexadentate ligand)
Ambidentate: can bind thru distinct atoms, e.G. NO2– (thru N or O), SCN– (via S or N)
Coordination Number (CN): Number of ligand donor atoms directly connected to principal atom.
Example: [Co(NH3)6]³+ → CN = 6
Coordination Sphere: The critical atom and ligands inside square brackets [ ].
Counter Ion: Ion out of doors the bracket balancing the charge.
Three. Nomenclature Rules
Cation is named first, then anion.
Ligands are named alphabetically before crucial atom.
Neutral ligands: NH3 = ammine, H2O = aqua, CO = carbonyl, NO = nitrosyl.
Negative ligands: end in –o (Cl– = chloro, CN– = cyano, OH– = hydroxo).
Prefixes: di-, tri-, tetra-, penta-, hexa-.
For complex ligands: bis-, tris-, tetrakis-.
1. Introduction
Coordination compounds are compounds wherein a vital metallic atom/ion is bonded to a
number of ions or impartial molecules (referred to as ligands).
These compounds are critical in organic structures (e.G. Hemoglobin, nutrition B12, chlorophyll)
and in industry (e.G. Catalysts, electroplating).
2. Important Terms
Coordination Entity: Central metallic ion + ligands connected.
Example: [Co(NH3)6]Cl3
Central Metal Atom/Ion: Lewis acid (accepts electron pair). Usually transition metals.
Ligands: Molecules/ions donating a couple of electrons to the vital atom.
Monodentate (donates through one atom): Cl–, H2O, NH3
Bidentate: en (ethane-1,2-diamine), C2O4²– (oxalate)
Polydentate: EDTA⁴– (hexadentate ligand)
Ambidentate: can bind thru distinct atoms, e.G. NO2– (thru N or O), SCN– (via S or N)
Coordination Number (CN): Number of ligand donor atoms directly connected to principal atom.
Example: [Co(NH3)6]³+ → CN = 6
Coordination Sphere: The critical atom and ligands inside square brackets [ ].
Counter Ion: Ion out of doors the bracket balancing the charge.
Three. Nomenclature Rules
Cation is named first, then anion.
Ligands are named alphabetically before crucial atom.
Neutral ligands: NH3 = ammine, H2O = aqua, CO = carbonyl, NO = nitrosyl.
Negative ligands: end in –o (Cl– = chloro, CN– = cyano, OH– = hydroxo).
Prefixes: di-, tri-, tetra-, penta-, hexa-.
For complex ligands: bis-, tris-, tetrakis-.
