Phenylmagnesium bromide

Phenylmagnesium bromide

Names
IUPAC name Bromido(phenyl)magnesium
Other names PMB, (bromomagnesio)benzene
Identifiers
CAS Number	100-58-3 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:51238
ChemSpider	10254417 Y
ECHA InfoCard	100.002.607
EC Number	202-867-2
PubChem CID	66852
CompTox Dashboard (EPA)	DTXSID3059214
InChI InChI=1S/C6H5.BrH.Mg/c1-2-4-6-5-3-1;;/h1-5H;1H;/q;;+1/p-1 N Key: ANRQGKOBLBYXFM-UHFFFAOYSA-M N InChI=1/C6H5.BrH.Mg/c1-2-4-6-5-3-1;;/h1-5H;1H;/q;;+1/p-1/rC6H5BrMg/c7-8-6-4-2-1-3-5-6/h1-5H Key: ANRQGKOBLBYXFM-ZAQPMBKGAV
SMILES Br[Mg]c1ccccc1
Properties
Chemical formula	C6H5MgBr
Molar mass	181.315 g·mol−1
Appearance	Colorless crystals
Density	1.14 g cm−3
Solubility in water	Reacts with water
Solubility	3.0M in diethyl ether, 1.0M in THF, 2.9M in 2-MeTHF
Acidity (pKa)	45 (conjugate acid)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Causes severe skin burns and serious eye damage, very flammable, volatile
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H314
Precautionary statements	P210, P233, P240, P241, P242, P243, P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P370+P378, P403+P235, P405, P501
Flash point	−45 °C (−49 °F; 228 K)
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	Phenyllithium Magnesium bromide Methylmagnesium chloride Dibutylmagnesium
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Phenylmagnesium bromide, with the simplified formula C₆H₅MgBr, is a magnesium-containing organometallic compound. It forms colorless crystals. It is commercially available as a solution in diethyl ether or tetrahydrofuran (THF). Phenylmagnesium bromide is a Grignard reagent. It is often used as a synthetic equivalent for the phenyl "Ph⁻" synthon.

Preparation

Phenylmagnesium bromide is prepared by reaction of bromobenzene with magnesium metal.

Phenylmagnesium bromide is commercially available as solutions of diethyl ether or THF. Laboratory preparation involves treating bromobenzene with magnesium metal, usually in the form of turnings. A small amount of iodine may be used to activate the magnesium to initiate the reaction.

Coordinating solvents such as ether or THF, are required to solvate (complex) the magnesium(II) center. The solvent must be aprotic since alcohols and water contain an acidic proton and thus react with phenylmagnesium bromide to give benzene. Carbonyl-containing solvents, such as acetone and ethyl acetate, are also incompatible with the reagent.

Structure

Structure of ether adducts of phenylmagnesium bromide where OR₂ an ether.

Although phenylmagnesium bromide is routinely represented as C₆H₅MgBr, the compound's structure is more complicated. Like most Grignard reagents, phenylmagnesium bromide is invariably observed as an adduct with various Lewis bases. Examples include the diethyl ether and tetrahydrofuran complexes C₆H₅MgBr[O(C₂H₅)₂]₂ and C₆H₅MgBr(OC₄H₈)₂, respectively. Thus, the Mg in those adducts is tetrahedral and obeys the octet rule. The Mg–O distances are 201 and 206 pm, and the Mg–C and Mg–Br distances are 220 pm and 244 pm, respectively in the diethyl ether complex. In their reactions of these complexes, these ether ligands dissociate.

Chemistry

Main article: Grignard reagent

Phenylmagnesium bromide is a strong nucleophile as well as a strong base. It can abstract even mildly acidic protons, thus the substrate must be protected where necessary. It often adds to carbonyls, such as ketones, aldehydes. With carbon dioxide, it reacts to give benzoic acid after an acidic workup. If three equivalents are reacted with phosphorus trichloride, triphenylphosphine can be made.