Reactions of Grignard Reagents with Tin-Corrole Complexes: Demetalation Strategy and σ‑Methyl/Phenyl Complexes

An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, methylmagnesium chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using methylmagnesium chloride in a representative corrolato-Sn­(IV)-chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn­(IV)-chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A3-corrole and one new corrolato Sn­(IV)­chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray structural analysis of the representative complexes. In the single-crystal X-ray data analyses, it was observed that the Sn–N and Sn–C bond distances are shorter than those in the similar tin porphyrin analogues. The 1H NMR spectrum of a representative σ-methyl complex exhibits peaks corresponding to σ-bonded methyl groups in the high field regions at −3.39 ppm.

本研究开发了一种高效、温和且一步法的合成策略，可将锡咔咯（tin-corroles）转化为对应结构的游离碱咔咯（free base corroles）。所用格氏试剂（Grignard reagent）为甲基氯化镁（methylmagnesium chloride），可高效实现锡咔咯的脱金属化反应。在优化后的反应条件下，以典型的咔咯根合锡(IV)氯化物配合物（corrolato-Sn(IV)-chloride complex）为底物时，几乎可实现完全脱锡。该反应方案已被证实对多种咔咯根合锡(IV)氯化物底物均具有普适性。然而，类似的格氏试剂——甲基溴化镁与苯基溴化镁——无法实现目标脱金属化反应，反而以优异收率生成了常规的σ-甲基配合物（σ-methyl complex）与σ-苯基配合物（σ-phenyl complex）。除两种新型σ-苯基配合物与三种新型σ-甲基配合物外，本研究还合成了一种新型A3-咔咯（A3-corrole）以及一种新型咔咯根合锡(IV)氯化物。所有配合物均通过多种光谱技术进行了全面表征，其中包括对典型配合物的单晶X射线结构分析（single-crystal X-ray structural analysis）。单晶X射线数据分析结果显示，该类配合物中的Sn–N与Sn–C键长均短于相似的锡卟啉类似物。典型σ-甲基配合物的氢谱（1H NMR）中，与σ键合甲基对应的信号峰出现在高场区域的-3.39 ppm处。