A clear step-by-step framework for naming complex ions, identifying coordination numbers, and stereoisomers.
Coordination Compounds form a vital cornerstone of Class 12 Inorganic Chemistry. Questions on IUPAC nomenclature, coordination number, isomerism, and bonding theories appear consistently in board exams, NEET, and JEE.
IUPAC Naming Rules: Name cations before anions. Within the coordination sphere, name ligands in alphabetical order before the central metal atom. Anionic ligands end in '-o' (e.g., chloro, cyano, hydroxo), neutral ligands use special names (aqua, ammine, carbonyl, nitrosom), and oxidation state of metal is written in Roman numerals in parentheses.
Isomerism in Coordination Complexes is divided into Structural Isomerism (Ionization, Solvate/Hydrate, Linkage, Coordination) and Stereoisomerism (Geometrical and Optical). Tetrahedral complexes do not show geometrical isomerism due to symmetrical ligand orientations.
For Octahedral Complexes [MA2B4] or [M(en)2Cl2], practice drawing cis and trans isomers. Non-superimposable mirror images of cis-isomers exhibit optical activity. Dr. Aarzoo Saini provides visual 3D model explanations at We-Gyaan Classes Roorkee to clarify stereochemistry.
Key Takeaways for Students
- Alphabetize ligands regardless of charge when writing IUPAC complex names.
- Identify linkage isomerism in ambidentate ligands (NO2 vs ONO, SCN vs NCS).
- Recognize optical activity in cis-isomers of octahedral complexes with bidentate ligands.
- Apply Crystal Field Theory to determine high-spin vs low-spin octahedral complexes.
Authored by Dr. Aarzoo Saini
Founder & Lead Educator at We-Gyaan Classes Roorkee, with over 20 years of teaching excellence in Science and Chemistry for Board Exams, NEET, JEE, and CUET.