Ruppert Heiko, Meister Arne, Pfretzschner Ronja, Vieira André Faria, Greb Lutz
Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg 69120, Germany.
J Am Chem Soc. 2024 Apr 24;146(16):11515-11522. doi: 10.1021/jacs.4c02446. Epub 2024 Apr 11.
Structural constraint approaches have been employed toward different ends in recent years, from augmenting the nucleophilicity in pyramidalized low-valent p-block compounds to enhancing the Lewis acidities at planarized tetravalent p-block elements. While previous studies exploited these effects separately, this work introduces a strategy to concatenate structural constraint approaches at individual stages of a reaction sequence in a row to unlock a synthetic path unattainable by conventional methodologies. The boosted nucleophilicity resulting from the constrained tetracoordinated calix[4]pyrrolato stannate(II) dianion enables the reductive formation of sterically unprotected acyclic aminocarbenes. These amino carbenes are stabilized at the concomitantly formed square-planar stannane(IV) as air-stable adducts. Transfer of the carbenes onto copper(I) by cooperativity of the calix[4]pyrrole ligand finalizes this protocol to hitherto unreported yet prototypical carbene complexes. Detailed spectroscopic and quantum theoretical analyses establish the synergy of structural constraints and element-ligand cooperation as the linchpin to this reaction path and its selectivity.
近年来，结构约束方法已被用于不同目的，从增强锥形低价p区化合物的亲核性到提高平面化四价p区元素的路易斯酸性。虽然以前的研究分别利用了这些效应，但这项工作引入了一种策略，在反应序列的各个阶段连续串联结构约束方法，以开辟一条传统方法无法实现的合成路径。由受限的四配位杯[4]吡咯锡酸（II）二价阴离子产生的增强亲核性能够还原形成空间上无保护的无环氨基卡宾。这些氨基卡宾以空气稳定加合物的形式稳定在同时形成的平面正方形锡（IV）上。通过杯[4]吡咯配体的协同作用将卡宾转移到铜（I）上，使该方案最终得到迄今未报道的典型卡宾配合物。详细的光谱和量子理论分析确定了结构约束与元素-配体协同作用的协同效应是这条反应路径及其选择性的关键。
