Oxidative Addition

Definition

Oxidative addition is a fundamental organometallic reaction in which a metal complex adds an atom or molecule across a covalent bond, resulting in the metal center increasing its oxidation state and coordination number. This process is crucial in understanding the reactivity of alkyl halides, organometallic coupling reactions, and the reactions of arylamines.

5 Must Know Facts For Your Next Test

1. Oxidative addition is a key step in the formation of Grignard reagents from alkyl halides, as the magnesium metal inserts into the carbon-halogen bond.
2. In organometallic coupling reactions, such as the Suzuki-Miyaura coupling, oxidative addition of an aryl halide to a transition metal catalyst is the first step in the catalytic cycle.
3. The reaction of arylamines with electrophiles, such as acyl chlorides, often proceeds via an oxidative addition mechanism to form new carbon-nitrogen bonds.
4. Oxidative addition can be facilitated by transition metal catalysts with low oxidation states, as they have available coordination sites to accommodate the added atoms or molecules.
5. The reverse process, reductive elimination, is also an important organometallic reaction that restores the original oxidation state and coordination number of the metal center.

Review Questions

• Explain how the oxidative addition mechanism contributes to the formation of Grignard reagents from alkyl halides.
  • In the formation of Grignard reagents, the magnesium metal undergoes oxidative addition to the carbon-halogen bond of the alkyl halide. This increases the oxidation state and coordination number of the magnesium, resulting in the formation of a nucleophilic organomagnesium species that can then participate in various synthetic transformations. The oxidative addition step is crucial for activating the alkyl halide and generating the reactive Grignard reagent.
• Describe the role of oxidative addition in the catalytic cycle of organometallic coupling reactions, such as the Suzuki-Miyaura coupling.
  • In organometallic coupling reactions, the first step of the catalytic cycle involves the oxidative addition of an aryl halide to the transition metal catalyst. This increases the oxidation state and coordination number of the metal center, allowing it to then undergo transmetalation with an organometallic reagent and subsequent reductive elimination to form the coupled product. The oxidative addition step is essential for activating the aryl halide and initiating the catalytic cycle, making it a crucial mechanistic step in these important carbon-carbon bond-forming reactions.
• Analyze how the oxidative addition mechanism can be applied to the reactions of arylamines with electrophiles, such as acyl chlorides, to form new carbon-nitrogen bonds.
  • The reaction of arylamines with electrophiles, like acyl chlorides, often proceeds via an oxidative addition mechanism. In this process, the transition metal catalyst first undergoes oxidative addition to the carbon-halogen bond of the acyl chloride, increasing its oxidation state and coordination number. This activated metal complex can then undergo nucleophilic attack by the arylamine, forming a new carbon-nitrogen bond. The oxidative addition step is key to activating the electrophile and facilitating the subsequent bond formation, allowing for the synthesis of new aryl-amide products through this organometallic reaction pathway.

Related terms

Oxidative State: The oxidation state of an atom or ion, which reflects the degree of oxidation of the species. Oxidative addition increases the oxidation state of the metal center.

Coordination Number: The number of atoms, ions, or molecules that are directly bonded to a central atom or ion. Oxidative addition increases the coordination number of the metal center.

Organometallic Reactions: Reactions involving compounds containing a carbon-metal bond, which are often facilitated by oxidative addition and other organometallic processes.