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

Abstract

In our experiments, 1:1 stoichiometric reaction between MgR 2 and diphenylamine produced the monomeric heteroleptic alkylmagnesium amides [RMgNPh 2(THF) 2] [R=Et 1 and i Pr 2]. Adding the stronger donor solvent HMPA (HMPAhexamethyl-phosphoramide) to compound 1 caused disproportionation resulting in a bisamidomagnesium compound [Mg(NPh 2) 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-N i Pr 2)(THF)] 2 [R=Ph 4, R=SiMe 3 5]. When the differently sized secondary amines, HNEt 2 and HN(SiMe 3) 2, were reacted with Grignard reagent EtMgBr, they produced diethylamino-bridging and bromo-bridging Hauser base [BrMg(μ-NEt 2)(HMPA)] 2 6 and [(Me 3Si) 2NMg(μ-Br)(OEt 2)] 2 7, respectively. Unexpectedly, the reaction of MgEt 2 and HN(SiMe 3) 2 in refluxing THF produced [(Me 3Si) 2NMg(μ-OEt)(THF)] 2 8. Additionally, we synthesized the first trinuclear magnesium compound [( t BuCC)(THF)Mg(μ-CC t Bu)(μ-N i Pr 2)Mg(μ-CC t Bu)(μ-N i Pr 2)Mg(THF)(CC t Bu)] 9, which exhibited both an electron-rich bridging ligand N i Pr 2 and electron-deficient bridging ligand CC t Bu. All of these new compounds ( 1– 9) were characterized by 1H-, 13C-, 31P-NMR, IR spectroscopy, mass spectrometry and X-ray crystallography.