Berthold Chantsalmaa, Maurer Johannes, Klerner Lukas, Harder Sjoerd, Buchner Magnus R
Fachbereich Chemie, Philipps-Universität Marburg, 35043, Marburg, Germany.
Inorganic and Organometallic Chemistry, Universität Erlangen-Nürnberg, Egerlandstrasse 1, 91058, Erlangen, Germany.
Angew Chem Int Ed Engl. 2024 Aug 26;63(35):e202408422. doi: 10.1002/anie.202408422. Epub 2024 Jul 11.
Attempts to create a novel Mg-Be bond by reaction of [(BDI*)MgNa] with Be[N(SiMe)] failed; BDI*=HC[(tBu)C=N(DIPeP)], DIPeP=2,6-EtC-phenyl. Even at elevated temperatures, no conversion was observed. This is likely caused by strong steric shielding of the Be center. A similar reaction with the more open CpBeCl gave in quantitative yield (BDI)MgBeCp* (1). The crystal structure shows a Mg-Be bond of 2.469(4) Å. Homolytic cleavage of the Mg-Be bond requires ΔH=69.6 kcal mol (cf. CpBe-BeCp 69.0 kcal mol and (BDI)Mg-Mg(BDI) 55.8 kcal mol). Natural-Population-Analysis (NPA) shows fragment charges: (BDI*)Mg +0.27/BeCp* -0.27. The very low NPA charge on Be (+0.62) compared to Mg (+1.21) and the strongly upfield Be NMR signal at -23.7 ppm are in line with considerable electron density on Be and the formal oxidation state assignment of Mg-Be. Despite this Mg-Be polarity, 1 is extremely thermally stable and unreactive towards H, CO, N, cyclohexene and carbodiimide. It reacted with benzophenone, azobenzene, phenyl acetylene, CO and CS. Reaction with 1-adamantyl azide led to reductive coupling and formation of an N-chain. The azide reagent also inserted in the Cp*-Be bond. The inertness of 1 is likely due to bulky ligands protecting the Mg-Be unit.
通过[(BDI*)MgNa]与Be[N(SiMe)]反应来创建新型Mg-Be键的尝试失败了；BDI*=HC[(tBu)C=N(DIPeP)]，DIPeP=2,6-EtC-苯基。即使在高温下，也未观察到转化。这可能是由于Be中心受到强烈的空间位阻屏蔽所致。与更为开放的CpBeCl进行的类似反应以定量产率得到了(BDI)MgBeCp* (1)。晶体结构显示Mg-Be键长为2.469(4) Å。Mg-Be键的均裂需要ΔH = 69.6 kcal·mol（参考CpBe-BeCp为69.0 kcal·mol以及(BDI)Mg-Mg(BDI)为55.8 kcal·mol）。自然布居分析（NPA）显示片段电荷：(BDI*)Mg为 +0.27/BeCp为 -0.27。与Mg(+1.21)相比，Be上极低的NPA电荷(+0.62)以及在 -23.7 ppm处强烈的高场Be NMR信号与Be上相当大的电子密度以及Mg-Be的形式氧化态归属一致。尽管存在这种Mg-Be极性，1却具有极高的热稳定性，并且对H、CO、N、环己烯和碳二亚胺无反应活性。它与二苯甲酮、偶氮苯、苯乙炔、CO和CS发生了反应。与1-金刚烷基叠氮化物反应导致还原偶联并形成了N链。叠氮试剂也插入到了Cp-Be键中。1的惰性可能归因于庞大的配体保护了Mg-Be单元。
