Chemistry:Dimethylmagnesium
Dimethylmagnesium is an organomagnesium compound with the chemical formula (CH
3)
2Mg. It is a white pyrophoric solid.[1][2] Dimethylmagnesium is used in the synthesis of organometallic compounds.
Preparation
Like other dialkylmagnesium compounds, dimethylmagnesium is prepared by adding dioxane to a solution of methylmagnesium halide:[3]
- 2 CH
3MgX + 2 dioxane ⇌ (CH
3)
2Mg + MgX
2(μ-dioxane)
2↓
In such procedures, the dimethylmagnesium exists as the ether adduct, not the polymer.[4]
Addition of 1,4-dioxane causes precipitation of solid MgX
2(μ-dioxane)
2, a coordination polymer.[4] This precipitation drives the Schlenk equilibrium toward (CH
3)
2Mg. Related methods have been applied to other dialkylmagnesium compounds.[5]
Dimethylmagnesium can also be prepared by combining dimethylmercury and magnesium.[6][7]
Calcium metal, magnesium metal and methyl iodide reacts in diethyl ether to produce dimethylmagnesium.[6]
- Ca + Mg + 2 CH
3I → CaI
2 + (CH
3)
2Mg
Properties
Single crystals can be obtained by recrystallization of crude dimethylmagnesium from trimethylgallium.[3] The structure of this compound has been determined by X-ray crystallography. The material is a polymer with the same connectivity as silicon disulfide, featuring tetrahedral magnesium centres, each surrounded by bridging methyl groups. The Mg-C distances are 223 pm. The Mg-Mg distances are 272 pm.[3][8]
Related compounds
The linear chain structure seen for dimethylmagnesium is also observed for diethylmagnesium and dimethylberyllium.[9] Di(tert-butyl)magnesium is however a dimer.[10]
References
- ↑ Cope, A. C. (1935). "The Preparation of Dialkylmagnesium Compounds from Grignard Reagents". J. Am. Chem. Soc. 57 (11): 2238–2240. doi:10.1021/ja01314a059.
- ↑ Anteunis, M. (1962). "Studies of the Grignard Reaction. II. Kinetics of the Reaction of Dimethylmagnesium with Benzophenone and of Methylmagnesium Bromide-Magnesium Bromide with Pinacolone". J. Org. Chem. 27 (2): 596–598. doi:10.1021/jo01049a060.
- ↑ 3.0 3.1 3.2 Stuhl, Christoph; Anwander, Reiner (2018). "Dimethylmagnesium revisited". Dalton Transactions 47 (36): 12546–12552. doi:10.1039/C8DT01542B. PMID 29790529.
- ↑ 4.0 4.1 Fischer, Reinald; Görls, Helmar; Meisinger, Philippe R.; Suxdorf, Regina; Westerhausen, Matthias (2019). "Structure–Solubility Relationship of 1,4-Dioxane Complexes of Di(hydrocarbyl)magnesium". Chemistry – A European Journal 25 (55): 12830–12841. doi:10.1002/chem.201903120. PMID 31328293. Bibcode: 2019ChEuJ..2512830F.
- ↑ Richard A. Andersen, Geoffrey Wilkinson (1979). "Bis[(Trimethylsilyl)Methyl] Magnesium". Inorg. Synth. 19: 262–265. doi:10.1002/9780470132500.ch61.
- ↑ 6.0 6.1 (in German) Houben-Weyl Methods of Organic Chemistry Vol. XIII/2a, 4th Edition Organometallic Compounds of Group II of the Periodic Table (except mercury), Georg Thieme Verlag, 2014, p. 215, ISBN 978-3-13-180654-3, https://books.google.com/books?id=cSqGAwAAQBAJ&pg=PA215
- ↑ Jane E. Macintyre (1994) (in German), Dictionary of Organometallic Compounds, CRC Press, p. 2273, ISBN 978-0-412-43060-2, https://books.google.com/books?id=3kYZDa6rBjYC&pg=PA2273
- ↑ Weiss, E. (1964). "Die Kristallstruktur des Dimethylmagnesiums". J. Organomet. Chem. 2 (4): 314–321. doi:10.1016/S0022-328X(00)82217-2.
- ↑ Snow, A.I.; Rundle, R.E. (1951). "Structure of Dimethylberyllium". Acta Crystallographica 4 (4): 348–52. doi:10.1107/S0365110X51001100. Bibcode: 1951AcCry...4..348S.
- ↑ Starowieyski, Kazimierz B.; Lewinski, Janusz; Wozniak, Robert; Lipkowski, Janusz; Chrost, Andrzej (2003). "Di- tert -butylmagnesium: Synthesis and Structure". Organometallics 22 (12): 2458–2463. doi:10.1021/om030091j.
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