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Chapter 111 Organometallic Compounds: Chapter 11.

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Presentation on theme: "Chapter 111 Organometallic Compounds: Chapter 11."— Presentation transcript:

1 Chapter 111 Organometallic Compounds: Chapter 11

2 Chapter 112 Organometallic Compounds Most metals are less electronegative than carbon In general a carbon bonded to a metal is nucleophilic and carbanion-like (C – ) Four major classes of organometallic compounds are: Organolithium compounds Grignard reagents Cuprates Organopalladium compounds

3 Chapter 113 Grignard & Lithium Reagents Grignard and lithium Organometallic reagents made by reacting a halide with elemental metal Mg essentially slides into C-halogen bond Li simply replaces halogen

4 Chapter 114 Grignard & Lithium Reagents Although the carbon–metal bonds are not completely ionic, organolithium compounds and Grignard reagents react as if the carbon portion were a carbanion Consider the reaction of a Grignard reagent with an ethylene oxide Ethylene oxide is a good way to extend a carbon chain by two carbons via use of halide to make organometallic cpd with negative charge on C

5 Chapter 115 Gilman Reagents Gilman reagents, also called organocuprates, are prepared from the reaction of an organolithium reagent with copper(I) iodide in diethyl ether or THF

6 Chapter 116 Gilman Reagents When a Gilman reagent reacts with an alkyl halide (except F - ) one of the alkyl groups replaces the halide Alkyl groups can substitute halogens attached to alkene or aromatic C with Gilman reagent; impossible with S N 1 or S N 2 reaction Mechanism unknown, probably radical

7 Chapter 117 Suzuki and Heck Reactions Various palladium catalysts substitute ordinary unfunctionalized alkenes for Br, I, or triflate (OT f ) leaving group attached to benzene or alkene (Heck). Reagent can even be made to substitute alkyl groups if a dialkoxyalkylborane reagent is used with it (Suzuki).

8 Chapter 118 Grubbs & Schrock Metathesis Terminal alkenes couple eliminating ethylene with rhodium catalyst (Grubbs). Terminal alkynes couple eliminating acetylene (ethyne) using molybdenum or tungsten catalyst (Schrock).

9 Chapter 119 Retrosynthetic Analysis: Using Ethylene Oxide (EO) Product has 2 extra C’s plus CN 2 extra C’s mean use EO Always work back to an ROH for EO analysis Retro EO addn removes 2 C’s and an OH Here CN has sub’d for an ROH-derived LG (leav grp) Make OTs the LG & derive the ROTs from ROH Cyclohexyl C  attacks EO to make this ROH

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