Isopropylmagnesium chloride

Last updated
Isopropylmagnesium chloride
IPrMgCl.png
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.012.680 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 213-947-1
PubChem CID
UNII
  • InChI=1S/C3H7.ClH.Mg/c1-3-2;;/h3H,1-2H3;1H;/q-1;;+2/p-1
    Key: IUYHWZFSGMZEOG-UHFFFAOYSA-M
  • C[CH-]C.[Mg+2].[Cl-]
Properties
C3H7ClMg
Molar mass 102.84 g·mol−1
Solubility Ethyl ether
Hazards
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-acid.svg
Danger
H225, H260, H314
P210, P223, P231+P232, P233, P240, P241, P242, P243, P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P335+P334, P363, P370+P378, P402+P404, P403+P235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Isopropylmagnesium chloride is an organometallic compound with the general formula (CH3)2HCMgCl. This highly flammable, colorless, and moisture sensitive material is the Grignard reagent derived from isopropyl chloride. It is commercially available, usually as a solution in tetrahydrofuran.

Contents

Synthesis and reactivity

Solutions of isopropylmagnesium chloride by treating isopropyl chloride with magnesium metal in refluxing ether: [1]

(CH3)2HCCl + Mg → (CH3)2HCMgCl

This reagent is used to prepare other Grignard reagents by transmetalation. [2] An illustrative reaction involves the generation of the Grignard reagent derived from bromo-3,5-bis(trifluoromethyl)benzene: [3]

(CH3)2HCMgCl + (CF3)2C6H3Br → (CH3)2HCCl + (CF3)2C6H3MgBr

Addition of one equivalent of LiCl to isopropylmagnesium chloride gives "Turbo Grignard" solutions, named so due to the increased rate and efficiency for transmetalation reactions. [4] [5]

Isopropylmagnesium chloride is also used to prepare isopropyl compounds, such as chlorodiisopropylphosphine: [6]

PCl3 + 2 (CH3)2CHMgCl → [(CH3)2CH]2PCl + 2 MgCl2

This reaction exploits the bulky nature of the isopropyl substituent.

Turbo-Grignard reagents

As initially reported by Knochel et al., [7] lithium chloride enhances the ability of isopropylmagnesium chloride toward transmetalation reactions. The more reactive species, a LiCl-iPrMgCl complex, is called a Turbo-Grignard reagent. These species are related to Turbo-Hauser bases, a family of magnesium amido compounds containing also LiCl. [8] "Turbo-Grignards", as they are often called, are aggregates with the formula [i-PrMgCl·LiCl]2. These species promote formation of aryl and heteroaryl Grignard reagents by halogen-magnesium exchange: [9]

fast, homogeneous: XC6H4Br + i−PrMgCl·LiCl → XC6H4MgCl·LiCl + i−PrBr

The traditional method for generating the aryl Grignard reagent proceeds less predictably:

slow, heterogeneous: XC6H4Br + Mg → XC6H4MgBr

Furthermore, traditional routes to Grignard reagents has limited functional group compatibility, whereas the Turbo-Grignard method tolerates other halides, some ester groups, and nitriles.

References

  1. ↑ Seyferth, Dietmar (2009-03-23). "The Grignard Reagents" . Organometallics. 28 (6): 1598–1605. doi:10.1021/om900088z. ISSN   0276-7333.
  2. ↑ Knochel, P.; Dohle, W.; Gommermann, N.; Kneisel, F. F.; Kopp, F.; Korn, T.; Sapountzis, I.; Vu, V. A. (2003). "Highly Functionalized Organomagnesium Reagents Prepared through Halogen–Metal Exchange". Angewandte Chemie International Edition. 42 (36): 4302–4320. doi:10.1002/anie.200300579. PMID   14502700.
  3. ↑ Johnnie L. Leazer Jr; Raymond Cvetovich (2005). "A Practical and Safe Preparation of 3,5-Bis(trifluoromethyl)acetophenone". Org. Synth. 82: 115. doi:10.15227/orgsyn.082.0115.
  4. ↑ Krasovskiy, Arkady; Knochel, Paul (2004-06-21). "A LiCl‐Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl‐ and Heteroarylmagnesium Compounds from Organic Bromides" . Angewandte Chemie International Edition. 43 (25): 3333–3336. doi:10.1002/anie.200454084. ISSN   1433-7851.
  5. ↑ Hermann, Andreas; Seymen, Rana; Brieger, Lukas; Kleinheider, Johannes; Grabe, Bastian; Hiller, Wolf; Strohmann, Carsten (2023-06-19). "Comprehensive Study of the Enhanced Reactivity of Turbo‐Grignard Reagents**". Angewandte Chemie International Edition. 62 (25). doi: 10.1002/anie.202302489 . ISSN   1433-7851.
  6. ↑ W. Voskuil; J. F. Arens (1968). "Chlorodiisopropylphosphine". Org. Synth. 48: 47. doi:10.15227/orgsyn.048.0047.
  7. ↑ Krasovskiy, A.; Knochel, P. (2004). "A LiCl-Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl- and Heteroarylmagnesium Compounds from Organic Bromides". Angew. Chem. Int. Ed. 43 (25): 3333–3336. doi:10.1002/anie.200454084. PMID   15213967.
  8. ↑ Li-Yuan Bao, Robert; Zhao, Rong; Shi, Lei (2015). "Progress and Developments in the turbo Grignard Reagent i-PrMgCl·LiCl: A Ten-Year Journey". Chemical Communications. 51 (32): 6884–6900. doi:10.1039/c4cc10194d. PMID   25714498.
  9. ↑ Knochel, Paul; Gavryushin, Andrei (2010). "Lithium Dichloro(1-methylethyl)-magnesate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01161. ISBN   978-0-471-93623-7.
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