The surface nature of Grignard reagent formation. Cyclopropylmagnesium bromide

Walborsky, H. M.; Zimmermann, Christoph

doi:10.1021/ja00039a007

Cited by 53 publications

(14 citation statements)

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“…Ultimately, the alkyl radical combines with MgX radical to give the Grignard complex. In recent years, investigations have focused on the nature of the alkyl radical precursors in Grignard formation reactions and have attempted to determine whether these species remain closely associated with the metal surface or diffuse freely in solution prior to radical addition. Most recently, investigators have studied the nature of the reactive sites on the metal surface, concluding that Grignard formation is strongly influenced by characteristics of the metal surface, and is likely initiated at crystal defects or impurities in the metal.…”

Section: Introductionmentioning

confidence: 99%

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI

Bare

Andrews

1998

J. Am. Chem. Soc.

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Magnesium atoms generated by laser ablation were reacted with methyl halides diluted (0.5% to 0.1%) in argon. Reaction products were trapped in a cryogenic argon matrix and analyzed by infrared spectroscopy. The primary reaction product, isolated Grignard molecule CH3MgX, and the secondary reaction products MgX, MgX2, MgH, MgH2, CH4, C2H6, CH2X, CH3MgCH3, XMgCH2, HMgCH3, and HMgCH2X were identified by isotopic (13C, D, and 26Mg) substitution and by correlation with B3LYP and BP86 isotopic frequency calculations. This investigation reports the first experimental evidence for the fluoride Grignard species, CH3MgF. Infrared absorptions were also observed for associated Grignard species.

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Section: Introductionmentioning

confidence: 99%

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI

Bare

Andrews

1998

J. Am. Chem. Soc.

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“…According to previous literature, the mechanism for Grignard reagent formation involved a single-electron transfer pathway. [56][57][58][59][60] A control experiment in the presence of one equivalent of free-radical scavengers, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) (compared with CBr bonds), was conducted, and no polymer was obtained with M-4 as the starting material. Notably, during the Ullmann coupling reaction based on surface synthesis, aryl halides are deposited onto the metal surface (e.g., Cu(111)), which allows the dissociation of their halide groups in a reaction catalyzed by the metal substrate.…”

Section: Resultsmentioning

confidence: 99%

Benzene Ring Knitting Achieved by Ambient‐Temperature Dehalogenation via Mechanochemical Ullmann‐Type Reductive Coupling

Chen

Fan

et al. 2021

Advanced Materials

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The current approaches capable of affording conjugated porous networks (CPNs) still rely on solution‐based coupling reactions promoted by noble metal complexes or Lewis acids, on‐surface polymerization conducted in ultrahigh‐vacuum environment at very high temperatures (>200 °C), or mechanochemical Scholl‐type reactions limited to electron‐rich substrates. To develop simple and scalable approaches capable of making CPNs under neat and ambient conditions, herein, a novel and complementary method to the current oxidative Scholl coupling processes is demonstrated to afford CPNs via direct aromatic ring knitting promoted by mechanochemical Ullmann‐type reactions. The key to this strategy lies in the dehalogenation of aromatic halides in the presence of Mg involving the formation of Grignard reagent intermediates. Products (Ph‐CPN‐1) obtained via direct CC bond formation between 1,2,4,5‐tetrabromobenzene (TBB) monomer feature high surface areas together with mesoporous architecture. The versatility of this approach is confirmed by the successful construction of various CPNs via knitting of the corresponding aromatic rings (e.g., pyrene and triphenylene), and even highly crystalline graphite product was obtained. The CPNs exhibit good electrochemical performance as the anode material in lithium‐ion batteries (LIBs). This approach expands the frontiers of CPN synthesis and provides new opportunities to their scalable applications.

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“…This leads to formation of the ethyl radical capable of migrating into the bulk of the reaction system 5 or being involved in a series of transformations on the metal surface. [43][44][45][46] Considering this configuration of the adsorbate molecule on the surface, the formation of the transition complex through bond rearrangement can be explained with ease assuming that the process pro ceeds by the molecular mechanism. 32, 33 The dipole moments µ of Mg n -L systems decrease with elongation of the Mg-L bond and asymptotically approach the dipole moment of isolated molecule L at R → ∞ (Fig.…”

Section: Resultsmentioning

confidence: 99%

Adsorption of solvent and oxidant molecules on magnesium surface: effect on the electronic structure and reactivity of magnesium in reactions of Grignard reagent formation

2008

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The effect of adsorption of the oxidant (EtBr) and aprotic dipolar solvent molecules on the electronic structure and properties of Mg n (n ≤ 50) clusters simulating the surface of metallic magnesium was studied by the B3PW91/6 31G(d) density functional method. It was found that the work function of an electron from the cluster monotonically decreases as the donor ability of the adsorbed molecules increases. The experimentally measured rate of the magnesium oxidation by EtBr correlates with the negative Mulliken charge density of the first coordination sphere of the surface adsorption site. The results obtained are in agreement with the experimentally determined work function of electron from metals during adsorption from the gas phase. Presumably, the rate limiting step of the Grignard reagent formation is the surface oxidation reaction.Reactions of oxidative dissolution of metals in aprotic media have been the subject of considerable litera ture. 1-7 A classical example of this reaction in a system including a metal, an organic or organoelement oxidant, and an aprotic dipolar solvent is the formation of the Grignard reagent RMgX:Although reaction (1) was discovered and quantita tively characterized more than a hundred years ago, its mechanism is still the matter of discussion. 8-15 In partic ular, the role of aprotic solvent that significantly facili tates the course of reaction (1) is still to be clarified. 16 Donor polar solvents can dissolve films of magnesium hydroxide 5 and/or products of reactions occurring on the metal surface, 9 thus making surfaces accessible to reac tants. In addition, this type of solvents can stabilize both intermediates and organometallic reaction products.The assumption that acceleration of oxidation reactions in the presence of a solvent is due to an increase in the solubility of the halide of the metal oxidized was also not substantiated. 16 The catalytic activity of the solvent in this reaction is also associated 17,18 with its ability to ac tivate the metal surface by affecting active sites on the surface.Numerous experimental data 7,19 obtained in the stud ies of metal oxidation by compounds with different chem ical composition and structure in aprotic solvents re vealed extremal dependences of the reaction rate on the donor numbers (DN SbCl 5 ) of the solvents. 20 The sol vent effect on the rate of oxidation reactions of various metals can be described 21,22 by a multiparameter equa tion including macroscopic and physicochemical char acteristics of the medium (in particular, the Kop pel-Palm nucleophilicity, polarity, the Hildebrandt sol ubility parameter, and the van der Waals radius of free solvent molecule 23 ). These correlations are based on the linear free energy relationship and the Hammett-Taft linear relations were proposed 12-14 in studies of the oxi dation of magnesium by p substituted phenyl halides; however, the mechanism of the process is still unknown.It is assumed 9 that the solvent adsorbed on a metal surface causes the work function of an electron from the m...

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The surface nature of Grignard reagent formation. Cyclopropylmagnesium bromide

Cited by 53 publications

References 1 publication

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI

Benzene Ring Knitting Achieved by Ambient‐Temperature Dehalogenation via Mechanochemical Ullmann‐Type Reductive Coupling

Adsorption of solvent and oxidant molecules on magnesium surface: effect on the electronic structure and reactivity of magnesium in reactions of Grignard reagent formation

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The surface nature of Grignard reagent formation. Cyclopropylmagnesium bromide

Cited by 53 publications

References 1 publication

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH3MgF, CH3MgCl, CH3MgBr, and CH3MgI

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH3MgF, CH3MgCl, CH3MgBr, and CH3MgI

Benzene Ring Knitting Achieved by Ambient‐Temperature Dehalogenation via Mechanochemical Ullmann‐Type Reductive Coupling

Adsorption of solvent and oxidant molecules on magnesium surface: effect on the electronic structure and reactivity of magnesium in reactions of Grignard reagent formation

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Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI

Formation of Grignard Species from the Reaction of Methyl Halides with Laser-Ablated Magnesium Atoms. A Matrix Infrared Study of CH₃MgF, CH₃MgCl, CH₃MgBr, and CH₃MgI