TYPE html> Chapter 5: Coordination Compounds - Shoorveer Notes

Chapter 5: Coordination

Complete Master Class & Notes

सफलता अंतिम नहीं है, असफलता घातक नहीं है: यह जारी रखने का साहस है जो मायने रखता है।
"Success is not final, failure is not fatal: it is the courage to continue that counts."
1. Introduction & Werner's Theory

Double Salts vs Coordination Compounds

  • Double Salts: Dissociate completely into simple ions when dissolved in water. Example: Mohr's salt, Potash alum.
  • Coordination Compounds: Do not dissociate into simple ions completely in water. They retain their identity. Example: K₄[Fe(CN)₆].

Werner's Theory

Metals possess two types of linkages (valencies):

  • Primary Valency: Ionizable, satisfied by negative ions. Corresponds to oxidation state (Dotted lines).
  • Secondary Valency: Non-ionizable, satisfied by ligands. Corresponds to coordination number (Solid lines). Decides geometry.
2. Ligands & Coordination Entity

Ligands and Their Types

Ligands act as Lewis bases (electron pair donors).

  • Unidentate: Bounds through a single donor atom (Cl⁻, H₂O, NH₃).
  • Didentate: Bounds through two donor atoms (ethane-1,2-diamine, oxalate).
  • Polydentate: Bounds through several donor atoms (EDTA⁴⁻ is hexadentate).
  • Chelating Ligand: Di/Polydentate ligand binding a single metal ion to form a ring (Chelate effect = extra stability).
  • Ambidentate Ligand: Can ligate through two different atoms (NO₂⁻, SCN⁻).
3. IUPAC Nomenclature

General Rules

  • Cation is named first in both positively and negatively charged coordination entities.
  • Ligands are named in alphabetical order before the metal.
  • Anionic ligands end in -o (chloro, cyanido). Neutral ligands remain same except aqua, ammine, carbonyl, nitrosyl.
  • If complex is an anion, metal name ends with -ate (ferrate, cuprate).

Examples

K₄[Fe(CN)₆] : Potassium hexacyanidoferrate(II) [Co(NH₃)₅Cl]Cl₂ : Pentaamminechloridocobalt(III) chloride
4. Isomerism

Structural Isomerism

  • Ionization: Exchange of ions between coordination and ionization sphere.
  • Linkage: Due to ambidentate ligands (NO₂ vs ONO).
  • Coordination: Interchange of ligands between cationic & anionic entities.
  • Hydrate: Water acts as ligand or water of hydration.

Stereoisomerism

  • Geometrical: cis (adjacent) and trans (opposite). fac and mer in [Ma₃b₃].
  • Optical: Chiral complexes, non-superimposable mirror images (dextro/laevo).
5. VBT & CFT Theories

Valence Bond Theory (VBT)

  • sp³: Tetrahedral (e.g., [NiCl₄]²⁻).
  • dsp²: Square Planar (e.g., [Ni(CN)₄]²⁻).
  • sp³d²: Octahedral, Outer orbital, high spin.
  • d²sp³: Octahedral, Inner orbital, low spin.

Crystal Field Theory (CFT)

Ligands are treated as point charges. Degeneracy of d-orbitals splits into t₂g (lower) and eg (higher) sets.

Spectrochemical Series:
I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO
  • Strong Field Ligands: Large splitting (Δ₀ > P). Electrons pair up. Low spin.
  • Weak Field Ligands: Small splitting (Δ₀ < P). Electrons jump up. High spin.
  • Colour: Due to d-d transition of electrons absorbing visible light.

📚 Additional Study Material

Master Coordination Compounds by practicing Previous Year Questions and reading deep-dive long notes.

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