MECHANISM OF THE GRIGNARD REAGENT FORMATION - PART 1 - THEORETICAL INVESTIGATIONS OF THE Mgn AND RMgn PARTICIPATION IN THE MECHANISM

Péralez, Eric; Négrel, Jean-Claude; Goursot, Annick; Chanon, Michel

doi:10.1515/mgmc.1999.22.3.185

Cited by 8 publications

(7 citation statements)

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“…Identification was based on the further reactions that occurred on warming to 30 K, changes in relative Be/CO concentration, 13 CO and C 18 O isotopic substitution, and ab initio calculations. Identification was based on the further reactions that occurred on warming to 30 K, changes in relative Be/CO concentration, 13 CO and C 18 O isotopic substitution, and ab initio calculations.…”

Section: Miscellaneous Reactions and Datamentioning

confidence: 99%

“…155 The reaction between the iodide R 2 C(SiMe 2 OMe)I and Mg in Et 2 O produces the chelated dialkylmagnesium Mg{C(SiMe 3 ) 2 (SiMe 2 OMe)} 2 34 and MgI 2 (OEt 2 ) 2 , presumably via the intermediacy of the Grignard reagent 28. X-ray structure analysis of 36 (R ¼ Ph) reveals that the S atoms are not coordinated to Mg. Racemic mixtures of the unsymmetrical substituted Mg alkyl Mg(Bu){CH[SPh][SiPh 2 (CH 2 NR 2 )]} (NR 2 ¼ 1-piperidyl, 1-pyrrolidyl) 37, which possesses a stereogenic metallated C atom, is obtained by deprotonation of an (aminomethyl)[(phenylthio)methyl]silane with MgBu n Bu s (eqn [13]). The Et 2 O is rapidly lost under vacuum.…”

Section: Preparationmentioning

confidence: 99%

“…Reaction of 79 with diphenylacetylene in THF also induces a ligand exchange reaction, giving the diphenylacetylene adduct [Mg 2 (PhC 2 Ph) 2 (THF)] 2 . The predicted NMR chemical shifts using the GIAO method give 13 On reaction with MeMgCl, the lithium triazine Li(THF) 2 {N[C(Ph)N] 2 }CBu t (Bu n ) yields the methylmagnesiodihydrotriazine 86 (eqn [18]). 263 The calculated geometries are in good agreement with experimental values for the corresponding THF complexes.…”

Section: Addition Compounds Of Magnesium With Unsaturated Organic Molmentioning

confidence: 99%

“…[6][7][8] The gas-phase RaC 2 À ion, which could be considered a radium(I) acetylide (and the only known organoradium species), has been produced with a Cs sputter-ion source. 11 Various low oxidation state aggregates with magnesium-magnesium bonds (e.g., MeMg 2 F, 12 MeMg n , 13 and (MeCl)Mg (4-21) 14 ) have been examined computationally as models of Grignard reagent formation, and cluster Grignard reagents PhMg 4 X (X¼ F, Cl, Br) have been prepared by metal-vapor synthesis. 11 Various low oxidation state aggregates with magnesium-magnesium bonds (e.g., MeMg 2 F, 12 MeMg n , 13 and (MeCl)Mg (4-21) 14 ) have been examined computationally as models of Grignard reagent formation, and cluster Grignard reagents PhMg 4 X (X¼ F, Cl, Br) have been prepared by metal-vapor synthesis.…”

Section: Introductionmentioning

confidence: 99%

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Alkaline Earth Organometallics

Hanusa

2014

Reference Module in Chemistry, Molecular Sciences and Chemical Engineering

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Section: Miscellaneous Reactions and Datamentioning

confidence: 99%

Section: Preparationmentioning

confidence: 99%

Section: Addition Compounds Of Magnesium With Unsaturated Organic Molmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alkaline Earth Organometallics

Hanusa

2014

Reference Module in Chemistry, Molecular Sciences and Chemical Engineering

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“…Furthermore, DFT calculations suggest that alkyl radicals could add to magnesium clusters and the species formed should display higher reducing power than magnesium clusters themselves. [123] These species, which result from the addition of carbon-centred radicals to zero-va-lent magnesium, correspond to Mg + species. In Scheme 1 these intermediates are represented by the structure 3.…”

Section: Introductionmentioning

confidence: 99%

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

et al. 2010

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Both SRN1‐type reactions and Grignard reagent formation are inhibited by trace amounts (with respect to the halide) of p‐dinitrobenzene (DNB) and other oxidising agents such as CuCl2 or dioxygen. Both are believed to be triggered by an electron‐transfer step. In this report we examine the patterns of reactivity shared by these two types of reaction. Although the two reactions display an amazing number of similarities, the chain character of the Grignard reaction mechanism has been rejected by major contributors to this field. We have performed new experiments to explore the inhibiting effect associated with the addition of trace amounts of p‐dinitrobenzene during Grignard reagent formation. This inhibition involves very reactive nanoparticles of magnesium prepared by metal vapour synthesis. The magnesium slurries studied, in the absence of p‐dinitrobenzene, display no induction period at all. If the p‐dinitrobenzene is added to the solution containing magnesium slurries 25 min before adding the organic halide (here bromobenzene), the reaction is neatly inhibited but, if one waits long enough, the Grignard reagent is nevertheless formed. If, however, the same trace amounts of p‐dinitrobenzene are diluted in the organic halide and this mixture is added to the magnesium slurries, the inhibiting effect is far less pronounced. The addition of the nBu4NBr salt drastically diminishes the inhibiting power of DNB. These observations, in addition to the ESR study of radical anions formed in THF by the reaction of magnesium nanoparticles and DNB with various polyaromatics, suggest a mechanism for the observed inhibitions that involves a series of reversible adsorptions of the present species. This adsorption would depend on both thermodynamic and kinetic factors. Thermodynamics would favour the adsorption of DNB radical anions but C–X bond cleavage of the less strongly adsorbed aromatic radical anions would provide a kinetic driving force for displacing the equilibria in the direction of Grignard reagent formation. Salt effects could operate by displacing the equilibrium – adsorbed DNB radical anion or dianion versus solvated radical anion (with the counterion nBu4N+) – to the right, accelerating therefore the liberation of active sites on the magnesium surface. It appears that the inhibiting effect of the same compound finds its origin in two different molecular series of events in SRN1 and in Grignard reagent formation. The heterogeneous character of the Grignard reagent makes it possible to envision the possibility of active sites even on nanoparticles, whereas the inhibition of the SRN1 mechanism by DNB occurs in homogeneous solution.

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Beryllium & Magnesium: Organometallic ChemistryBased in part on the article Beryllium & Magnesium: Organometallic Chemistry by E. Alexander Hill which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Saulys

Hill

2005

Encyclopedia of Inorganic Chemistry

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Victor Grignard found in 1900 that solutions of organomagnesium halides form easily in the reaction of an organic halide with magnesium metal in diethyl ether. These Grignard reagents undergo useful reactions with many kinds of substrates. This discovery ushered in a new era in organometallic chemistry and provided chemists with a powerful and versatile reagent for synthesis of a wide variety of organic and organometallic compounds. This article discusses Grignard reagents in the broader context of organomagnesium chemistry. Preparatory methods surveyed include direct reaction of organic halides with the metal, exchange reactions with other organometallic compounds, as well as carbo‐ and hydrometalations. The current level of understanding of the mechanism of Grignard formation is summarized. The formation and reactivity of unusual species such as cluster Grignard reagents, for example, RMg 4 X (R = organic group, and X = halide) and polymagnesium compounds, for example, Ru[C 5 (MgCl) 5 ] 2 are also discussed. The bonding and structure of organomagnesium compounds (as well as that of beryllium analogues) as described by diffraction methods, thermochemical data, colligative properties, spectroscopic (vibrational, nuclear magnetic, and electronic) measurements, kinetic studies, mass spectrometry, and theoretical methods are outlined. The most prominent chemical property of organomagnesium compounds is their ability to deliver an effectively ‘anionic’ organic group with nucleophilic properties. As alkylating reagents, their important reactions include nucleophilic displacement of less basic leaving groups from saturated carbon atoms or other elements, addition to carbonyl groups and other unsaturated functions, and nucleophilic substitution at the acyl group of carboxylic acid derivatives. This broad array of substrates is surveyed, as are the effects of solvents and catalysts on reactivity. Less conspicuous reactions with wholly or predominantly inorganic substrates are also considered. Electron transfer reactions where organomagnesium compounds act as reductants are discussed. Organoberyllium compounds are more difficult to prepare and are less nucleophilic than their magnesium counterparts. These features, together with their high toxicity, have limited their utility. Methods of preparation, as well as descriptions of bonding, structure, and reactivity patterns are presented. Of special note are recent advances in cyclopentadienyl beryllium chemistry, as well as the advent of beryllium–silicon chemistry.

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MECHANISM OF THE GRIGNARD REAGENT FORMATION - PART 1 - THEORETICAL INVESTIGATIONS OF THE Mgn AND RMgn PARTICIPATION IN THE MECHANISM

Cited by 8 publications

References 48 publications

Alkaline Earth Organometallics

Alkaline Earth Organometallics

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

Beryllium & Magnesium: Organometallic ChemistryBased in part on the article Beryllium & Magnesium: Organometallic Chemistry by E. Alexander Hill which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

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MECHANISM OF THE GRIGNARD REAGENT FORMATION - PART 1 - THEORETICAL INVESTIGATIONS OF THE Mgn AND RMgn PARTICIPATION IN THE MECHANISM

Cited by 8 publications

References 48 publications

Alkaline Earth Organometallics

Alkaline Earth Organometallics

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

Beryllium & Magnesium: Organometallic ChemistryBased in part on the article Beryllium & Magnesium: Organometallic Chemistry by E. Alexander Hill which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

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About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism