isopropylmagnesium chloride
{{Chembox
|ImageFile = IPrMgCl.png
|Section1={{Chembox Identifiers
|CASNo = 1068-55-9
|CASNo_Ref = {{cascite|correct|CAS}}
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = MN8G5FEJ5J
|PubChem = 101955
|EC_number = 213-947-1
|ChemSpiderID = 10620969
|StdInChI=1S/C3H7.ClH.Mg/c1-3-2;;/h3H,1-2H3;1H;/q-1;;+2/p-1
|StdInChIKey = IUYHWZFSGMZEOG-UHFFFAOYSA-M
|SMILES = C[CH-]C.[Mg+2].[Cl-] }}
|Section2={{Chembox Properties
|C=3|H=7|Cl=1|Mg=1
|SolubleOther = Ethyl ether}}
|Section3={{Chembox Hazards
|GHSPictograms = {{GHS02}}{{GHS05}}
|GHSSignalWord = Danger
|HPhrases = {{H-phrases|225|260|314}}
|PPhrases = {{P-phrases|210|223|231+232|233|240|241|242|243|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|335+334|363|370+378|402+404|403+235|405|501}}
}}
}}
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.
Synthesis and reactivity
Solutions of isopropylmagnesium chloride by treating isopropyl chloride with magnesium metal in refluxing ether:{{Cite journal |last=Seyferth |first=Dietmar |date=2009-03-23 |title=The Grignard Reagents |url=https://pubs.acs.org/doi/10.1021/om900088z |journal=Organometallics |language=en |volume=28 |issue=6 |pages=1598–1605 |doi=10.1021/om900088z |issn=0276-7333}}
:{{chem2|(CH3)2HCCl + Mg → (CH3)2HCMgCl}}
This reagent is used to prepare other Grignard reagents by transmetalation.{{cite journal|author1=Knochel, P. |author2=Dohle, W. |author3=Gommermann, N. |author4=Kneisel, F. F. |author5=Kopp, F. |author6=Korn, T. |author7=Sapountzis, I. |author8=Vu, V. A. |title=Highly Functionalized Organomagnesium Reagents Prepared through Halogen–Metal Exchange|journal=Angewandte Chemie International Edition|year=2003|volume=42|issue=36 |pages=4302–4320|doi=10.1002/anie.200300579|pmid=14502700}} An illustrative reaction involves the generation of the Grignard reagent derived from bromo-3,5-bis(trifluoromethyl)benzene:{{cite journal|title=A Practical and Safe Preparation of 3,5-Bis(trifluoromethyl)acetophenone|author=Johnnie L. Leazer Jr |author2=Raymond Cvetovich |journal=Org. Synth.|year=2005|volume=82|page=115|doi=10.15227/orgsyn.082.0115}}
:(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.{{Cite journal |last=Krasovskiy |first=Arkady |last2=Knochel |first2=Paul |date=2004-06-21 |title=A LiCl‐Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl‐ and Heteroarylmagnesium Compounds from Organic Bromides |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.200454084 |journal=Angewandte Chemie International Edition |language=en |volume=43 |issue=25 |pages=3333–3336 |doi=10.1002/anie.200454084 |issn=1433-7851}}{{Cite journal |last=Hermann |first=Andreas |last2=Seymen |first2=Rana |last3=Brieger |first3=Lukas |last4=Kleinheider |first4=Johannes |last5=Grabe |first5=Bastian |last6=Hiller |first6=Wolf |last7=Strohmann |first7=Carsten |date=2023-06-19 |title=Comprehensive Study of the Enhanced Reactivity of Turbo‐Grignard Reagents** |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.202302489 |journal=Angewandte Chemie International Edition |language=en |volume=62 |issue=25 |doi=10.1002/anie.202302489 |issn=1433-7851|doi-access=free }}
Isopropylmagnesium chloride is also used to prepare isopropyl compounds, such as chlorodiisopropylphosphine:{{cite journal|author1=W. Voskuil |author2=J. F. Arens |title=Chlorodiisopropylphosphine|journal=Org. Synth.|year=1968|volume=48|page=47|doi=10.15227/orgsyn.048.0047}}
: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.,{{cite journal|author1= Krasovskiy, A.|author2= Knochel, P. |journal=Angew. Chem. Int. Ed.|year=2004|volume=43 |issue= 25 | pages= 3333–3336|title= A LiCl-Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl- and Heteroarylmagnesium Compounds from Organic Bromides | doi= 10.1002/anie.200454084|pmid= 15213967 }} lithium chloride, isopropylmagnesium 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.{{cite journal|doi=10.1039/c4cc10194d |title=Progress and Developments in the turbo Grignard Reagent i-PrMgCl·LiCl: A Ten-Year Journey |date=2015 |last1=Li-Yuan Bao |first1=Robert |last2=Zhao |first2=Rong |last3=Shi |first3=Lei |journal=Chemical Communications |volume=51 |issue=32 |pages=6884–6900 |pmid=25714498 }} "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:{{cite book |doi=10.1002/047084289X.rn01161 |chapter=Lithium Dichloro(1-methylethyl)-magnesate |title=Encyclopedia of Reagents for Organic Synthesis |date=2010 |last1=Knochel |first1=Paul |last2=Gavryushin |first2=Andrei |isbn=978-0-471-93623-7 }}
:fast, homogeneous: {{chem2|XC6H4Br + i\sPrMgCl·LiCl -> XC6H4MgCl·LiCl + i\sPrCl + MgBrCl}}
The traditional method for generating the aryl Grignard reagent proceeds less predictably:
:slow, heterogeneous: {{chem2|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.