Organometallic Compounds Compounds that contain _________________bond (______): Examples of M include ________(Grignard reagents), _____________. ____________ carbon: Reacts with _____________ carbon and forms a new _________________. Nomenclature: Similar naming to substituted metals (alkyl metals or alkyl metal halides). Organomagnesium: Grignard reagent. CH3Li: Methyl lithium. CH3MgBr: Methyl MgBr. Organometallic Compounds Properties: High Reactivity: Organmometallics are usually kept in organic solvents due to their very high reactivity. Reacts especially with H2O, O2, etc. RMgX + H2O RMgX + O2 Organometallic Compounds Structure: Ionic Character: R-M = R- M+ NaR and KR are __________. Electronegativities: Na: 0.9, K: 0.8, C: 2.5 CH3F LiR and MgR have a sigma bond between the carbon atom and the metal. These are ________compounds. Electronegativities: Li: 1.0, Mg: 1.2 CH3Li Organometallic Compounds Reactivity: Bases act as ___________ Basicity: Simple carbanions are _____________. Carbon is not very electronegative compared to nitrogen or oxygen. RLi + HOR _________ RMgX + HOR ______________ RLi or RMgX _________ be used in the presence of _____________, such as –___________ General Mechanisms 1. Nucleophilic Substitution: R2CuLi reaction with alkyl halides or tosylates. Nu C LG LG 2. Nucleophilic Addition: RLi or RMgX with aldehydes or ketones. O Nu Nu C C 3. Nucleophilic Acyl Substitution: RLi or RMgX with esters. O O Nu Nu C LG C LG O Nu C LG Organolithium Reagents RX + 2 Li RLi + Li+X(X = I, Br, Cl) Reaction Type: Alkyl halides react with lithium metal. Other Group I metals (Na, K) can be used instead of lithium. Solvents: Alkyl group can be. R can be. Halide Reactivity: Organolithium Reagents RX + 2 Li RLi + Li+X(X = I, Br, Cl) Limitations: Organolithium, RLi, is _____________for an SN1 or SN2 with alkyl halides or tosylates. This gives __________________ reaction or other side reactions. Organomagnesium Reagents Et2O RX + Mg RMgX (X = I, Br, Cl) Reaction Type: Alkyl halides react with magnesium metal. Solvents: Alkyl group can be primary, secondary or tertiary. R can be alkyl, vinyl or aryl. Halide Reactivity: Organomagnesium Reagents Et2O RX + Mg RMgX (X = I, Br, Cl) Limitations: Organomagnesium, RMgX is ___________for SN1 or SN2 with alkyl halides or tosylates. In these situations, RMgX gives ___________ reactions and other side reactions. Common Reactions with Carbonyl Groups: Aldehydes/Ketones: RLi and RMgX react with the _____________ Organomagnesium Reagents Et2O RX + Mg RMgX (X = I, Br, Cl) Common Reactions with Carbonyl Groups: Aldehydes/Ketones: RLi and RMgX react with the carbonyl (C=O) to create _____________. Addition to methanal (formaldehyde) __________. Addition to other aldehydes ______________. Addition to ketones ____________. The acidic work-up intermediate metal alkoxide salt alcohol via a simple _________ reaction. Organomagnesium Mechanism RLi or RMgX R C H RLi or RMgX H O H O R C H R' RLi or O RMgX C R' C H O H R H H R' R' C O H R H R' R' R" C R" OH C H R OH C O H R C R OH Esters Reaction Type: Requires ________ equivalents of organolithium or Grignard reagents. Product: _______________ Tertiary alcohol contains ______________ alkyl groups via a _____________which reacts with the second equivalent of the organometallic. Since the ketone is ________________ than the ester, the reaction _______ stop at a ketone. Grignard Reactions R’ = Alkyl, vinyl, aryl. X = Cl, Br, I R’X RCHO H2CO Mg/Ether RCOR HCO2Et RCN R’MgX (EtO)2CO H2O or acidic H O RCO2Et CO2 Organocopper Reagents Et2O 2 RLi + CuX R2CuLi + Li+X(X = I, Br, Cl) Lithium Dialkylcuprates, R2CuLi _____ organolithiums with a copper (I) halide. Solvents: The alkyl group is usually ____________. _____________are prone to decomposition. R can be _________________________. Halide Reactivity: Organocopper Reagents Et2O 2 RLi + CuX R2CuLi + Li+X(X = I, Br, Cl) Limitations: Organocuprates, R2CuLi, are __________ and can be reacted with _____________________ to give alkanes. Organocopper Reagents Alkane Synthesis Using R2CuLi: R2CuLi + R’-X R-R’ + RCu + LiX Reaction Type: Creation of new C-C bonds. ______________are best, otherwise an elimination reaction can occur. The R’ group in the halide can be ______________ The R group of the cuprate can be ______________ Although the mechanism looks like a _________ reaction, it is more complex and is not well understood. Organozinc Reagents Et2O RX + Zn RZnX (X = I, Br, Cl) Reaction Type: RZnX is made in a similar fashion as RZnX is _________ reactive than RLi or RMgX with aldehydes and ketones. The most common application of organozinc reagents is in the Simmons-Smith Reaction. Organozinc Reagents Synthesis of Cyclopropanes using RZnX Known as the Simmons-Smith Reaction Et2O ICH2I + Zn I-CH2-ZnI Cu Et2O I-CH2-ZnI + =—R + ZnI2 Iodomethyl zinc iodide is usually prepared using Zn and activated with Cu. Iodomethyl zinc iodide reacts with an alkene to give a Organozinc Reagents Synthesis of Cyclopropanes using RZnX Reaction is __________specific with respect to the alkene. Mechanism is ____________. Substituents that are _______ in the alkene are ______ in the cyclopropane. Substituents that are______ in the alkene are ______ in the cyclopropane. CH3 I-CH2ZnI ZnI2 CH3 Et2 O I-CH2ZnI ZnI2 CH3 CH3 Et2 O Organozinc Reagents Mechanism of the Simmons-Smith Reaction + ZnI2 CH2 I CH2 ZnI Reaction is ________________. Both new C-C bonds are formed simultaneously. Nucleophilic C=C causes loss of iodide leaving group. Electrons from nucleophilic C-Zn bond form the other C-C bond. Acetylenic Reagents B:- (B:- = NaNH2) R—CΞC—H R—CΞC:- + B-H Or B:- (B:- = R’MgX) R—CΞC—H R—CΞC:- MgX + R’-H Reaction Type: Reacts as a _______________ 3 important groups of reactions where nucleophiles attack electrophilic C atoms. Product is new C-C bonds. Acetylenic Mechanism RC CLi or RC CMgX RC CLi or RC CMgX RC H C C H H CLi R' O H C H O R' R' C C R' O CMgX H H H or RC O C H C H H R' R' C R" O O H R" C OH OH OH R" C=O in aldehydes/ketones alcohols. Addition to methanal (formaldehyde) gives __________________. Addition to other aldehydes gives ______________________. Addition to ketones gives tertiary _____________.