Synthesis, characterization and crystal structures of alkyl-, alkynyl-, alkoxo- and halo-magnesium amides

In our experiments, 1:1 stoichiometric reaction between MgR2 and diphenylamine produced the monomeric heteroleptic alkylmagnesium amides [RMgNPh2(THF)2] [R=Et 1 and iPr 2]. Adding the stronger donor solvent HMPA (HMPAhexamethyl-phosphoramide) to compound 1 caused disproportionation resulting in a bisamidomagnesium compound [Mg(NPh2)2(HMPA)2] 3. The stoichiometric reaction between bis(diisopropylamido)-magnesium and different substituted acetylenes HCCR in THF solution produced two dimeric amidomagnesium acetylide compounds [(RCC)Mg(μ-NiPr2)(THF)]2 [R=Ph 4, R=SiMe35]. When the differently sized secondary amines, HNEt2 and HN(SiMe3)2, were reacted with Grignard reagent EtMgBr, they produced diethylamino-bridging and bromo-bridging Hauser base [BrMg(μ-NEt2)(HMPA)]26 and [(Me3Si)2NMg(μ-Br)(OEt2)]27, respectively. Unexpectedly, the reaction of MgEt2 and HN(SiMe3)2 in refluxing THF produced [(Me3Si)2NMg(μ-OEt)(THF)]28. Additionally, we synthesized the first trinuclear magnesium compound [(tBuCC)(THF)Mg(μ-CCtBu)(μ-NiPr2)Mg(μ-CCtBu)(μ-NiPr2)Mg(THF)(CCtBu)] 9, which exhibited both an electron-rich bridging ligand NiPr2 and electron-deficient bridging ligand CCtBu. All of these new compounds (1–9) were characterized by 1H-, 13C-, 31P-NMR, IR spectroscopy, mass spectrometry and X-ray crystallography.