--- title: "Elementary Steps of Catalysis: Oxidative Addition and Insertion" description: "Many organometallic catalytic cycles combine oxidative addition, reductive elimination, migratory insertion and beta-hydride elimination. Tracking ligand charges and donations gives the formal oxidati" canonical: https://lightmysky.com/learn/science/elementary-steps-of-catalysis-oxidative-addition-and-insertion-mt_VVLGGh8QZ_ source: https://lightmysky.com/learn/science/elementary-steps-of-catalysis-oxidative-addition-and-insertion-mt_VVLGGh8QZ_.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Elementary Steps of Catalysis: Oxidative Addition and Insertion Many organometallic catalytic cycles combine oxidative addition, reductive elimination, migratory insertion and beta-hydride elimination. Tracking ligand charges and donations gives the formal oxidation-state and electron-count changes. State which ligands remain bound and whether another step occurs before assigning the final count. Subject: Science · Area: Chemistry · Ages 20 to 22 Page: https://lightmysky.com/learn/science/elementary-steps-of-catalysis-oxidative-addition-and-insertion-mt_VVLGGh8QZ_ ## Ready when they can - States the change in oxidation state and electron count for oxidative addition and for its reverse - Distinguishes migratory insertion from simple addition and identifies which ligand moves - Recognises beta-hydride elimination and explains what structural feature makes it possible - Describes common conditions that favor oxidative addition and explains how ligand dissociation can prepare a saturated complex ## Lesson: The small steps behind big catalytic cycles You have counted ligand donations. An X-type ligand is assigned charge -1 in ionic counting and donates 2 electrons there, or 1 in neutral counting. In conventional mononuclear two-electron oxidative addition, A-B is cleaved and both fragments bind one metal as X-type ligands. Examples include H2 and aryl halides. Reductive elimination reverses this: two bound groups couple into a molecule that leaves. Track each step separately from ligand association or dissociation. In CO migratory insertion, a metal-bound alkyl (M-R) migrates onto coordinated CO, forming an acyl (M-C(O)R). The reacting ligands need a suitable arrangement, commonly cis, meaning adjacent coordination positions. One X-type alkyl and one 2-electron CO become one X-type acyl. Before another ligand binds, the metal oxidation state is unchanged and the count falls by 2. Direct association adds a ligand without this ligand-to-ligand bond formation. **Example.** Suppose a 16-electron M(II) complex undergoes two-electron oxidative addition with other ligands unchanged. Two new X-type ligands donate 4 electrons in ionic counting, but M(IV) has 2 fewer d electrons than M(II). The net count increases by 2 to 18. Reductive elimination reverses both changes: oxidation state falls by 2 and count falls by 2. *(drawing: Conventional two-electron changes, with all other ligands unchanged. OS means the metal oxidation state.)* Many two-electron oxidative additions are favored by low-valent, electron-rich metal centres with accessible coordination capacity. A saturated 18-electron precursor may first lose a ligand, giving a reactive species that then adds A-B. These are common conditions, not a universal rule that every starting complex must already be unsaturated. Substrate, metal, geometry and mechanism also matter. Beta-hydride elimination moves H from a metal alkyl's beta carbon to the metal, forming an alkene. The alpha carbon binds M; the beta carbon is next. It normally needs a beta C-H bond, an accessible site and syn-coplanar M-C-C-H geometry: these atoms lie in one plane, with M and H on the same side of C-C. If the alkene stays bound, oxidation state is unchanged and the count rises by 2. This reverses alkene insertion into M-H, not CO insertion. CO insertion can leave a coordination position available, but solvent or another ligand may occupy it before the product is observed. A 2-electron donor then restores the count lost in insertion. Follow the actual ligand inventory: a low count alone does not prove a geometrically accessible site. A trapped product with no free site need not mean the insertion analysis was mistaken. **Recap.** State the step and ligand inventory. Two-electron OA and RE change oxidation state; insertion does not. Check beta hydrogens, geometry and any later ligand binding. *Original lesson, questions and flashcards on formal organometallic reaction steps, written for this learning collection.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Organometallic Ligands: Carbonyls, Phosphines and Hapticity](https://lightmysky.com/learn/science/organometallic-ligands-carbonyls-phosphines-and-hapticity-mt_JXYSQDYlJ-) ## Opens up - [Catalytic Cycles: Tracing Steps Around a Closed Loop](https://lightmysky.com/learn/science/catalytic-cycles-tracing-steps-around-a-closed-loop-mt_FmsXXdFRNC) - [Cross-Coupling in Practice: Choosing Ligand, Base and Conditions](https://lightmysky.com/learn/science/cross-coupling-in-practice-choosing-ligand-base-and-conditions-mt_y2vF6EDb2X)