key term - Reductive Elimination

Definition

Reductive elimination is a fundamental organometallic reaction in which two ligands attached to a metal center are removed as a new covalent bond is formed between them. This process is crucial in various organic transformations, including cross-coupling reactions and the synthesis of arylamines.

5 Must Know Facts For Your Next Test

1. Reductive elimination is a key step in many cross-coupling reactions, such as the Suzuki-Miyaura, Negishi, and Stille couplings, where it facilitates the formation of a new carbon-carbon bond.
2. In the context of arylamine synthesis (topic 24.8), reductive elimination is involved in the final step, where the metal-bound aryl and amino groups are eliminated to form the desired arylamine product.
3. The mechanism of reductive elimination typically involves the metal center adopting a more electron-rich, lower oxidation state configuration, which facilitates the removal of the two ligands.
4. The reductive elimination step is often the rate-limiting step in many cross-coupling reactions, as it requires the proper alignment of the two ligands to be eliminated.
5. The choice of metal, ligands, and reaction conditions can significantly influence the efficiency and selectivity of the reductive elimination step, making it an important area of study in organometallic chemistry.

Review Questions

• Explain the role of reductive elimination in the context of organometallic coupling reactions (topic 10.7).
  • In the context of organometallic coupling reactions (topic 10.7), reductive elimination is a crucial step that facilitates the formation of a new carbon-carbon bond. After the oxidative addition of the two coupling partners to the metal center and any necessary transmetalation steps, the reductive elimination step removes the two ligands as a new covalent bond is formed between them. This reductive elimination step is often the rate-limiting step in these cross-coupling reactions, as the proper alignment of the two ligands is required for the process to occur efficiently. The choice of metal, ligands, and reaction conditions can significantly influence the success of the reductive elimination step, making it an important area of study in this field of organic chemistry.
• Describe how reductive elimination is involved in the synthesis of arylamines (topic 24.8).
  • In the synthesis of arylamines (topic 24.8), reductive elimination is the key final step that forms the desired arylamine product. After the aryl and amino groups have been bound to the metal center, the reductive elimination process removes these two ligands, allowing them to combine and create the new carbon-nitrogen bond. The reductive elimination step is crucial in this transformation, as it facilitates the release of the arylamine product from the metal complex. The efficiency and selectivity of this reductive elimination step can be influenced by factors such as the choice of metal, ligands, and reaction conditions, making it an important consideration in the development of arylamine synthesis methods.
• Evaluate the significance of reductive elimination in the broader context of organic synthesis and mechanistic understanding in organometallic chemistry.
  • Reductive elimination is a fundamentally important reaction in organometallic chemistry, as it represents a key step in many crucial organic transformations. Beyond its role in organometallic coupling reactions (topic 10.7) and arylamine synthesis (topic 24.8), reductive elimination is a central concept that underpins our mechanistic understanding of a wide range of organometallic processes. By facilitating the formation of new covalent bonds through the removal of ligands from a metal center, reductive elimination allows for the construction of complex organic molecules and the release of desired products. A deep understanding of the factors that influence the efficiency and selectivity of reductive elimination is therefore crucial for the continued development of powerful synthetic methodologies in organic chemistry. Furthermore, the study of reductive elimination provides valuable insights into the fundamental reactivity and bonding patterns of organometallic complexes, which is essential for advancing the field of organometallic chemistry as a whole.

Related terms

Oxidative Addition:

The reverse of reductive elimination, where a substrate adds across a metal center, increasing the metal's oxidation state and coordination number.

Transmetalation:

The transfer of a ligand from one metal center to another, a key step in many cross-coupling reactions.

Migratory Insertion: The insertion of a substrate into a metal-ligand bond, leading to the formation of a new carbon-carbon or carbon-heteroatom bond.