Electron accountancy

Aims
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

L ligands (2e donors)

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

X ligands (1e donors)

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

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

 VN = number of X ligands + charge on complex

 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

 LBN = sum of L and X ligands