Spring 2011 Dr. HalliganCHM 236

• Organometallic Compounds

Chapter 11

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

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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 organomagnesiumcompounds

However, these organometallic compounds cannot be prepared from compounds containing acidic groups (OH, NH2, NHR, SH, C=CH, CO2H)

Let’s draw a reaction to show how this happens:

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Coupling Reactions

Preparation of the Gilman reagent:

Example of carbon–carbon formation using the Gilman reaction:

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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 SN1 or SN2 reactions?

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Gilman reagents can replace halogens in compounds containing other functional groups:

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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: Transstereochemistry

Regeneration of the catalyst: Undergoes oxidative addition to bromobenzene