The direct synthesis of organocalcium compounds (heavy Grignard reagents) by the reduction of organyl halides with activated calcium powder succeeded in a straightforward manner for organic bromides and iodides that are bound at sp²‐hybridized carbon atoms. Extension of this strategy to alkyl halides was very limited, and only the reduction of trialkylsilylmethyl bromides and iodides with activated calcium allowed the isolation of the corresponding heavy Grignard reagents. Substitution of only one hydrogen atom of the methylene moiety by a phenyl or methyl group directed this reduction toward the Wurtz‐type coupling and the formation of calcium halide and the corresponding C−C coupling product. The stability of the methylcalcium and benzylcalcium derivatives in ethereal solvents suggests an unexpected reaction behavior of the intermediate organyl halide radical anions. Quantum chemical calculations verify a dependency between the ease of preparative access to organocalcium complexes and the C−I bond lengths of the organyl iodides. The bulkiness of the trialkylsilyl group is of minor importance. Chloromethyltrimethylsilane did not react with activated calcium; however, halogen‐exchange reactions allowed the isolation of [Ca(CH₂SiMe₃)(thf)₃(μ‐Cl)]₂. Furthermore, the metathetical approach of reacting [Ca(CH₂SiMe₃)I(thf)₄] with KN(SiMe₃)₂ and the addition of N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (pmdeta) allowed the isolation of heteroleptic [CaCH₂SiMe₃{N(SiMe₃)₂}(pmdeta)]. In the reaction of this derivative with phenylsilane, the trimethylsilylmethyl group proved to be more reactive than the bis(trimethylsilyl)amido substituent.

中文翻译：

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重格氏试剂的直接合成：挑战，局限性和衍生化

通过活化钙粉还原有机卤化物直接合成有机钙化合物（重度格氏试剂），对于结合在sp ^2上的有机溴化物和碘化物，以直接的方式获得了成功。杂交的碳原子。将该策略扩展至卤代烷非常有限，只有用活化钙还原三烷基甲硅烷基甲基溴和碘化物才能分离出相应的重质格氏试剂。苯基或甲基仅取代亚甲基部分的一个氢原子，使这种还原反应趋向于Wurtz型偶联，并形成卤化钙和相应的C-C偶联产物。甲基钙和苄基钙衍生物在醚溶剂中的稳定性表明中间体有机基卤化物自由基阴离子具有出乎意料的反应行为。量子化学计算证实了制备有机钙络合物的难易程度与有机碘化物的C–I键长度之间的依赖性。三烷基甲硅烷基的庞大性次要。氯甲基三甲基硅烷不与活化钙反应；但是，卤素交换反应可以分离出[Ca（CH₂ SiMe ₃）（thf）₃（μ-Cl）] ₂。此外，[Ca（CH ₂ SiMe ₃）I（thf）₄ ]与KN（SiMe ₃）_2反应并添加N，N，N'，N''，N'' -五甲基二亚乙基三胺（pmdeta）的复分解方法）可以分离出[CaCH ₂ SiMe ₃ {N（SiMe ₃）₂}（pmdeta）]。在该衍生物与苯基硅烷的反应中，三甲基甲硅烷基甲基被证明比双（三甲基甲硅烷基）酰胺基取代基更具反应性。