Transcript Organometallic Compounds
Fall 2011
Chapter 11
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Organometallic Compounds Dr. Halligan CHM 236
Ch. 11 Overview
• Organolithium and Grignard Reagents • Coupling reactions with Gilman reagents • Palladium-Catalyzed Coupling reactions including the Suzuki and Heck • Alkene Metathesis: Reactions with Grubb’s and Schrock’s catalysts
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Organometallic Compounds
An organic compound containing a carbon –metal bond Organolithium compounds and organomagnesium compounds are two of the most common organometallic compounds 4
Preparation of Organolithium Compounds
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Preparation of Organomagnesium Compounds
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Alkyl halides, vinyl halides, and aryl halides can all be used to form organolithium and organomagnesium compounds However, these organometallic compounds cannot be prepared from compounds containing acidic groups (OH, NH 2 , NHR, SH, C=CH, CO 2 H) Let’s draw a reaction to show how this happens: 8
Coupling Reactions
Preparation of the Gilman reagent: Example of carbon –carbon formation using the Gilman reaction: 9
Gilman reagents can be used to prepare compounds that cannot be prepared by using nucleophilic substitution reactions: Why can’t these compounds be prepared by S N 1 or S N 2 reactions?
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Gilman reagents can replace halogens in compounds containing other functional groups: 11
The Heck Reaction
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The Stille Reaction
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The Suzuki Coupling
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Mechanism of the Suzuki Coupling Reaction
Oxidative addition: Pd (0) to Pd (II):
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Hydroxide exchange:
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Transmetallation: Reductive elimination:
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Mechanism of the Heck Coupling Reaction
Oxidative addition: Pd (0) to Pd (II):
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Complex formation: Insertion:
complex
complex
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Elimination: Trans stereochemistry Regeneration of the catalyst: Undergoes oxidative addition to bromobenzene
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