Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany.
J Am Chem Soc. 2019 Sep 4;141(35):13931-13940. doi: 10.1021/jacs.9b06879. Epub 2019 Aug 20.
The hitherto unknown homoleptic tetramethylaluminate complex [Sc(AlMe)] could be obtained by reacting the ate complex [LiScMe(thf)] with AlMe in the cold. It cocrystallizes with AlMe as [Sc(AlMe)(AlMe)] and decomposes at ambient temperature in -pentane via multiple C-H bond activations to the mixed methyl/methylidene complex [Sc(μ-CH)(μ-CH)(AlMe)(AlMe)]. Donor-induced methylaluminate cleavage of [Sc(AlMe)(AlMe)] produced [ScMe] in good yield, which could be derivatized with trimethyltriazacyclononane (MeTACN) to form the structurally characterizable [(MeTACN)ScMe]. Additionally, half-sandwich complex [CpSc(AlMe)] and sandwich complex [CpSc(AlMe)] were accessible by salt metathesis reactions from [Sc(AlMe)(AlMe)] and KCp* (Cp* = CMe). Sc NMR spectroscopy was applied as a significant probe to evidence the existence of [ScMe]. Compounds [(MeTACN)ScMe] (+624.6 ppm) and [ScMe(thf)] (+601.7 ppm) gave large Sc NMR shifts, revealing the strong deshielding effect of the σ-bonded alkyl ligands on the scandium nuclei. Ultimately, cationized [Sc(AlMe)(AlMe)] was employed in isoprene polymerization, leading to polymers in high yields (>95%) and with high (>90%) -1,4-polyisoprene content.
hitherto 未知的同核四甲基铝配合物 [Sc(AlMe)] 可以通过将 ate 配合物 [LiScMe(thf)] 与 AlMe 在冷反应中获得。它与 AlMe 共结晶为 [Sc(AlMe)(AlMe)]，并在 -戊烷中于环境温度下通过多次 C-H 键活化分解为混合甲基/亚甲基配合物 [Sc(μ-CH)(μ-CH)(AlMe)(AlMe)]。供体诱导的 [Sc(AlMe)(AlMe)] 中甲基铝酸盐的裂解以高产率生成 [ScMe]，后者可以与三甲基三嗪环壬烷 (MeTACN) 衍生化形成结构可表征的 [(MeTACN)ScMe]。此外，通过盐交换反应从 [Sc(AlMe)(AlMe)] 和 KCp*（Cp* = CMe）可以获得半夹心配合物 [CpSc(AlMe)] 和夹心配合物 [CpSc(AlMe)]。 Sc NMR 光谱被用作证明 [ScMe] 存在的重要探针。化合物 [(MeTACN)ScMe]（+624.6 ppm）和 [ScMe(thf)]（+601.7 ppm）给出了较大的 Sc NMR 位移，表明 σ 键合的烷基配体对钪核有很强的去屏蔽效应。最终，阳离子化的 [Sc(AlMe)(AlMe)] 用于异戊二烯聚合，得到高产率（>95%）和高（>90%）-1,4-聚异戊二烯含量的聚合物。
