Ionisation von Organomagnesium‐Verbindungen, III. UV‐Spektroskopischer Nachweis des carbanionoiden Charakters in Äther gelöster benzylischer Organomagnesium‐Verbindungen

Ebel, H.; Wagner, Burkhard O.

doi:10.1002/cber.19711040136

Cited by 22 publications

(3 citation statements)

References 37 publications

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“…Although we conducted experiments at a concentration of 1 in THF of about 0.17 M , it seems unlikely that ionisation of 5 accounts for the observed dark‐red colour; note that we did not find 6 . In fact, diphenylmethylmagnesium bromide in Et 2 O is colourless ( λ max = 298 nm26a) and the observed λ max for the colourless solution of triphenylmethylmagnesium bromide in Et 2 O (318 nm26a) is presumably due to impurities rather than to ionisation of an organomagnesium compound 26a. Upon addition of 2 mol‐equiv.…”

Section: Resultsmentioning

confidence: 98%

The Grignard Reagent Formation Reaction of 2‐Chloro‐1,1,1‐triphenylethane Revisited

Bickelhaupt¹,

Newcomb

DeZutter

et al. 2008

Eur J Org Chem

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The reaction of 2-chloro-1,1,1-triphenylethane (1) with magnesium in THF has been reinvestigated. The reaction produced a dark-red solution and after deuterolysis with D 2 O, 1,1,1-triphenylethane (2; 16 %), 2-D-1,1,1-triphenylethane (3; 52 %) and 1,1,2-triphenylethene (4; 26 %) were isolated. Rate constants for phenyl migration in the 2,2,2-triphenylethyl radical were measured directly between 23°C and 55°C; the reaction is described by log k = 11.2 -7.5/2.3 RT [kcal/mol] and the rate constant for rearrangement at 20°C is

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Section: Resultsmentioning

confidence: 98%

The Grignard Reagent Formation Reaction of 2‐Chloro‐1,1,1‐triphenylethane Revisited

Bickelhaupt¹,

Newcomb

DeZutter

et al. 2008

Eur J Org Chem

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“…The fact that the signal of the benzylic protons of 4a has an AB pattern indicates that the structure must possess an unsymmetrical environment for these protons, and in addition, it must be quite rigid as otherwise, time averaging would make them equivalent as is normally observed for organomagnesium reagents which rapidly exchange bonds between magnesium, carbon, and other ligands [14]. In very dilute solutions, 4b predominates (vide infra), and it is colorless like dibenzylmagnesium; in THF solution, the UV absorption maximum of dibenzylmagnesium is at 277 nm [20]. This interpretation is supported by the './(CH) coupling constant of 126.7 Hz for the benzylic methylene group which is indicative of sp 195 hybridization.…”

Section: Resultsmentioning

confidence: 99%

OLIGOMERIC 1,2-DIHYDRO-1-MAGNESACYCLOBUTA[a]NAPHTHALENE

Nijbacker¹,

Goedheijt²,

Kanter³

et al. 2002

Main Group Metal Chemistry

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l,2-Dihydro-l-magnesacyclobuta[a]naphthalene (4), a mixed benzylic/aromatic diorganylmagnesium reagent, was prepared from the corresponding dihalide and magnesium in THF, followed by removal of MgBrCl with 1,4-dioxane. It is the first example of its kind which is soluble in THF and was shown (UV, NMR, degree of association) to establish an equilibrium between a highly polar oligomer 4a and a less highly associated and more conventional diorganylmagnesium 4b. 121Brought to you by | Purdue University Libraries Authenticated Download Date | 5/27/15 6:22 AM Friedrich Bickelhaupt et al. Oligomeric 1,2-Hydro-1 -Magnesacyclobuta[a]Naphthalene EXPERIMENTAL GeneralAll manipulations involving organometallic compounds were carried out in fully sealed glassware using standard high vacuum techniques. Solvents were dried by distillation from liquid Na/K alloy after predrying on NaOH. Magnesium was sublimed twice before use. 1 -Bromo-2-methylnaphthalene (Aldrich) and Λ'-bromosuccinimide (NBS, from ACROS) were commercially available. NMR spectra were measured on a Bruker AC 200 spectrometer ('H NMR: 200 MHz; 13 C NMR: 50.3 MHz) and on a Bruker MSL 400 spectrometer ('H NMR: 400.1 MHz; 13 C NMR: 100.6 MHz); the assignments are based on NOE difference and 2D measurements. GCMS analyses were performed on a HP 5890 GC/ 5970 MS combination, operating at 70 eV and equipped with a Chrompack BP1 (QSGE) 50 mJ 0.25 mm column. HRMS measurements were performed on a Finnigan MAT 90 mass spectrometer under EI conditions. UV/VIS spectra were recorded on a Beckman DU-64 spectrophotometer. l-Bromo-2-chloromethylnaphthalene (5) The synthesis of 5 was performed in analogy to that reported for 2a [11]. l-Bromo-2bromomethylnaphthalene was prepared by light induced radical bromination of l-bromo-2methylnaphthalene with 1.

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“…This band lies between absorption bands of ionic organometallic compounds in the range 420-470 nm and those of organomagnesium derivatives with predominantly covalent Mg-C bonds in the range 280-300 nm [38,39]. Thus, the bonds in complexes of PX with a magnesium atom (or cluster Mg n ) are neither purely ionic not covalent, but have intermediate structure.…”

Section: Polymers Containing Organometallic Unitsmentioning

confidence: 88%

Metal‐Containing Polymers: Cryochemical Synthesis, Structure, and Physicochemical Properties

Трахтенберг¹,

Герасимов²

2004

Metal–Polymer Nanocomposites

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Ionisation von Organomagnesium‐Verbindungen, III. UV‐Spektroskopischer Nachweis des carbanionoiden Charakters in Äther gelöster benzylischer Organomagnesium‐Verbindungen

Cited by 22 publications

References 37 publications

The Grignard Reagent Formation Reaction of 2‐Chloro‐1,1,1‐triphenylethane Revisited

The Grignard Reagent Formation Reaction of 2‐Chloro‐1,1,1‐triphenylethane Revisited

OLIGOMERIC 1,2-DIHYDRO-1-MAGNESACYCLOBUTA[a]NAPHTHALENE

Metal‐Containing Polymers: Cryochemical Synthesis, Structure, and Physicochemical Properties

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