Sigmund Lukas M, Engels Eliane, Richert Nick, Greb Lutz
Ruprecht-Karls-Universität Heidelberg, Anorganisch-Chemisches Institut Im Neuenheimer Feld 270 Heidelberg 69120 Germany.
Freie Universität Berlin, Anorganische Chemie Fabeckstraße 34-36 Berlin 14195 Germany
Chem Sci. 2022 Sep 7;13(37):11215-11220. doi: 10.1039/d2sc03054c. eCollection 2022 Sep 28.
Forcing tetracoordinate atoms into planar configuration represents a promising concept for enhanced reactivity of p-block element-based systems. Herein, the synthesis, characterization, and reactivity of calix[4]pyrrolato gallates, constituting square planar-coordinated gallium(iii) atoms, are reported. Unusual structural constraint-induced Lewis acidity against neutral and anionic donors is disclosed by experiment and rationalized by computations. An energetically balanced dearomatization/rearomatization of a pyrrole unit enables fully reversible metal-ligand cooperative capture of CO. While alcohols are found unreactive against the gallates, a rapid and selective OH-bond activation can be triggered upon protonation of the ligand. Secondary ligand-sphere modification adds a new avenue to structurally-constrained complexes that unites functional group tolerance with unconventional reactivity.
将四配位原子强制成平面构型是提高基于p区元素体系反应活性的一个有前景的概念。本文报道了杯[4]吡咯镓酸盐的合成、表征及反应活性，该化合物含有平面正方形配位的镓(III)原子。通过实验揭示了由不寻常的结构限制引起的对中性和阴离子供体的路易斯酸性，并通过计算进行了合理化解释。吡咯单元在能量上平衡的去芳香化/再芳香化使得能够完全可逆地通过金属-配体协同捕获CO。虽然发现醇类对镓酸盐无反应，但配体质子化后可引发快速且选择性的OH键活化。二级配体球修饰为结构受限的配合物开辟了一条新途径，将官能团耐受性与非常规反应活性结合在一起。
