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Dimethylmagnesium
Chemical compound From Wikipedia, the free encyclopedia
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Dimethylmagnesium is an organomagnesium compound with the chemical formula (CH3)2Mg. It is a white pyrophoric solid.[1][2] Dimethylmagnesium is used in the synthesis of organometallic compounds.
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Preparation
Like other dialkylmagnesium compounds, dimethylmagnesium is prepared by adding dioxane to a solution of methylmagnesium halide:[3]
- 2 CH3MgX + 2 dioxane ⇌ (CH3)2Mg + MgX2(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 MgX2(μ-dioxane)2, a coordination polymer.[4] This precipitation drives the Schlenk equilibrium toward (CH3)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 CH3I → CaI2 + (CH3)2Mg
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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]
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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
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