Oberdorf Kai, Hanft Anna, Ramler Jacqueline, Krummenacher Ivo, Bickelhaupt F Matthias, Poater Jordi, Lichtenberg Crispin
Department of Inorganic Chemistry, Julius-Maximilians-Universität, Würzburg, Am Hubland, 97074, Würzburg, Germany.
Department of Theoretical Chemistry, ACMM, Vrije Universiteit, Amsterdam, The Netherlands.
Angew Chem Int Ed Engl. 2021 Mar 15;60(12):6441-6445. doi: 10.1002/anie.202015514. Epub 2021 Jan 28.
The controlled release of well-defined radical species under mild conditions for subsequent use in selective reactions is an important and challenging task in synthetic chemistry. We show here that simple bismuth amide species [Bi(NAr ) ] readily release aminyl radicals [NAr ] at ambient temperature in solution. These reactions yield the corresponding hydrazines, Ar N-NAr , as a result of highly selective N-N coupling. The exploitation of facile homolytic Bi-Pn bond cleavage for Pn-Pn bond formation was extended to higher homologues of the pnictogens (Pn=N-As): homoleptic bismuth amides mediate the highly selective dehydrocoupling of HPnR to give R Pn-PnR . Analyses by NMR and EPR spectroscopy, single-crystal X-ray diffraction, and DFT calculations reveal low Bi-N homolytic bond-dissociation energies, suggest radical coupling in the coordination sphere of bismuth, and reveal electronic and steric parameters as effective tools to control these reactions.
在温和条件下可控释放明确的自由基物种以供后续用于选择性反应，这是合成化学中一项重要且具有挑战性的任务。我们在此表明，简单的铋酰胺物种[Bi(NAr ) ]在溶液中于室温下能轻易释放氨基自由基[NAr ]。这些反应通过高度选择性的N-N偶联生成相应的肼，即Ar N-NAr 。利用容易发生的Bi-Pn均裂键裂解来形成Pn-Pn键，这一方法扩展到了氮族元素（Pn = N - As）的更高同系物：均配型铋酰胺介导HPnR的高度选择性脱氢偶联反应，生成R Pn-PnR 。通过核磁共振（NMR）和电子顺磁共振（EPR）光谱分析、单晶X射线衍射以及密度泛函理论（DFT）计算表明，Bi-N均裂键离解能较低，表明在铋的配位球中存在自由基偶联，并揭示了电子和空间参数是控制这些反应的有效工具。
