Phenylmagnesium bromide

Phenylmagnesium bromide
	; Complex with ethers
	; Complex with diethyl ether
Names
	IUPAC name Bromido(phenyl)magnesium
	Other names PMB, (bromomagnesio)benzene [citation needed]
Identifiers
CAS Number	100-58-3 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:51238;
ChemSpider	10254417 ;
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 Key: ANRQGKOBLBYXFM-UHFFFAOYSA-M ; 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	181.31 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 2Me-THF
Acidity (pKa)	45 (conjugate acid)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	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). verify (what is ?) Infobox references

Phenylmagnesium bromide, with the simplified formula C
₆H
₅MgBr, is a magnesium-containing organometallic compound. 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 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.^[1]

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

Although phenylmagnesium bromide is routinely represented as C
₆H
₅MgBr, the molecule is more complex. The compound invariably forms an adduct with two OR
₂ ligands from the ether or THF solvent. Thus, the Mg is tetrahedral and obeys the octet rule. The Mg–O distances are 201 and 206 pm whereas the Mg–C and Mg–Br distances are 220 pm and 244 pm, respectively.^[2]

Chemistry

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.^[1]^[3] 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.

References

^ ^a ^b Robertson, D. L. (2007-01-03). "Grignard Synthesis: Synthesis of Benzoic Acid and of Triphenylmethanol". MiraCosta College. Retrieved 2008-01-25.
^ Stucky, G. D.; Rundle, R. E. (1963). "The Structure of Phenylmagnesium Bromide Diethyletherate and the Nature of Grignard Reagents". J. Am. Chem. Soc. 85 (7): 1002–1003. doi:10.1021/ja00890a039.
^ Bachmann, W. E.; Hetzner, H. P. (1955). "Triphenylcarbinol". Organic Syntheses; Collected Volumes, vol. 3, p. 839.

[robertson-1] Robertson, D. L. (2007-01-03). "Grignard Synthesis: Synthesis of Benzoic Acid and of Triphenylmethanol". MiraCosta College. Retrieved 2008-01-25.

[2] Stucky, G. D.; Rundle, R. E. (1963). "The Structure of Phenylmagnesium Bromide Diethyletherate and the Nature of Grignard Reagents". J. Am. Chem. Soc. 85 (7): 1002–1003. doi:10.1021/ja00890a039.

[3] Bachmann, W. E.; Hetzner, H. P. (1955). "Triphenylcarbinol". Organic Syntheses; Collected Volumes, vol. 3, p. 839.

[1]