Module B2

Ligands and Nomenclature

Concept Overview

Organometallic nomenclature introduces specific terms:

Hapticity ( $\eta$ notation): The number of contiguous atoms in a ligand directly coordinated to the metal.
- $\eta^1$ -alkyl: one carbon coordinated
- $\eta^5$ -cyclopentadienyl: all five carbons coordinated
- $\eta^6$ -benzene: all six carbons coordinated
Bridging Ligands ( $\mu$ notation): A ligand shared between two or more metal centers (e.g., $\mu_2$ -CO bridges two metals).
Nomenclature Rules: List ligands alphabetically, specify hapticity before ligand name, name the metal with oxidation state in parentheses.

Key Equations

This module focuses on nomenclature conventions rather than mathematical equations. Refer to the Ligand Gallery below for electron contribution counts.

Worked Examples

Determine the IUPAC name for $[Fe(\eta^5\text{-}C_5H_5)_2]$ .

Common Misconceptions

❌ Misconception

Hapticity (η) is the same as denticity.

✅ Correction

Denticity = number of distinct coordinate bonds from non-contiguous donor atoms (e.g., EDTA). Hapticity = contiguous coordination of a continuous π-electron system.

Interactive Visual

Click any ligand to see its hapticity, electron contribution, and bonding description:

Methyl (CH₃⁻)

Hapticity

η¹

Electrons

1 (cov) / 2 (ionic)

Charge

−1

σ-donor only. Forms a single M–C bond.

Formative Quiz

Question 1

What is the hapticity of the ethylene ligand in Zeise's salt,

[PtCl_3(\eta^2\text{-}C_2H_4)]^-

Connections

Builds on

B1History and General Characteristics

Feeds into

B3The 18-Electron Rule

Module B2

Ligands and Nomenclature

Concept Overview

Organometallic nomenclature introduces specific terms:

Hapticity ( $\eta$ notation): The number of contiguous atoms in a ligand directly coordinated to the metal.
- $\eta^1$ -alkyl: one carbon coordinated
- $\eta^5$ -cyclopentadienyl: all five carbons coordinated
- $\eta^6$ -benzene: all six carbons coordinated
Bridging Ligands ( $\mu$ notation): A ligand shared between two or more metal centers (e.g., $\mu_2$ -CO bridges two metals).
Nomenclature Rules: List ligands alphabetically, specify hapticity before ligand name, name the metal with oxidation state in parentheses.

Key Equations

This module focuses on nomenclature conventions rather than mathematical equations. Refer to the Ligand Gallery below for electron contribution counts.

Worked Examples

Determine the IUPAC name for $[Fe(\eta^5\text{-}C_5H_5)_2]$ .

Common Misconceptions

❌ Misconception

Hapticity (η) is the same as denticity.

✅ Correction

Denticity = number of distinct coordinate bonds from non-contiguous donor atoms (e.g., EDTA). Hapticity = contiguous coordination of a continuous π-electron system.

Interactive Visual

Click any ligand to see its hapticity, electron contribution, and bonding description:

Methyl (CH₃⁻)

Hapticity

η¹

Electrons

1 (cov) / 2 (ionic)

Charge

−1

σ-donor only. Forms a single M–C bond.

Formative Quiz

Question 1

What is the hapticity of the ethylene ligand in Zeise's salt,

[PtCl_3(\eta^2\text{-}C_2H_4)]^-

Connections

Builds on

B1History and General Characteristics

Feeds into

B3The 18-Electron Rule

Ligands and Nomenclature

Concept Overview

Key Equations

Worked Examples

Naming a Metallocene Derivative

Common Misconceptions

Interactive Visual

Methyl (CH₃⁻)

Formative Quiz

Connections

Ligands and Nomenclature

Concept Overview

Key Equations

Worked Examples

Naming a Metallocene Derivative

Common Misconceptions

Interactive Visual

Methyl (CH₃⁻)

Formative Quiz

Connections