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Electron accountancy


This Lesson will cover:

  • Revision of electron counting methods
  • The Covalent Bond Classification as an alternative method
  • Simple classes of ligand and bond ambiguities
  • Curly arrow conventions in complexes
  • Composite ligands
  • Formal oxidation state and the d-electron count
  • Coordination number and ambiguities

Classes of ligandEdit

L ligands (2e donors)Edit

  • PR3, N2, C2H4, CO, H2, C2H2
  • observed as neutral

X ligands (1e donors)Edit

  • H, halides, R (alkyl), Ar (aryl), COR (acyl), OR (alkoxides), NR2
  • observed as anions

Composite ligandsEdit

Electron countingEdit

The number of electrons donated by the metal = its group number.

Valence Number (VN)

VN = number of X ligands + charge on complex

Coordination Number (CN)

CN = number of atoms bonded to the metal CN = number of electron pairs added to the metal CN = number of ligands bonded to the metal

Ligand Bond Number (LBN)

LBN = sum of L and X ligands