Sorochkina Kristina, Chernichenko Konstantin, Zhivonitko Vladimir V, Nieger Martin, Repo Timo
Department of Chemistry, University of Helsinki, A. I. Virtasen aukio 1, 00014, Helsinki, Finland.
Chemical Process Research and Development Janssen Pharmaceutica, Turnhoutseweg 30, 2340, Beerse, Belgium.
Chemistry. 2022 Nov 2;28(61):e202201927. doi: 10.1002/chem.202201927. Epub 2022 Aug 31.
Ortho-phenylene-bridged phosphinoborane (2,6-Cl Ph) B-C H -PCy 1 was synthesized in three steps from commercially available starting materials. 1 reacts with H or H O under mild conditions to form corresponding zwitterionic phosphonium borates 1-H or 1-H O. NMR studies revealed both reactions to be remarkably reversible. Thus, when exposed to H , 1-H O partially converts to 1-H even in the presence of multiple equivalents of water in the solution. The addition of parahydrogen to 1 leads to nuclear spin hyperpolarization both in dry and hydrous solvents, confirming the dissociation of 1-H O to free 1. These observations were supported by computational studies indicating that the formation of 1-H and 1-H O from 1 are thermodynamically favored. Unexpectedly, 1-H O can release molecular hydrogen to form phosphine oxide 1-O. Kinetic, mechanistic, and computational (DFT) studies were used to elucidate the unique "umpolung" water reduction mechanism.
邻亚苯基桥连的膦硼烷(2,6-Cl Ph)B-C₆H₄-PCy₂ 1由市售原料经三步合成。1在温和条件下与H₂或H₂O反应形成相应的两性离子鏻硼酸酯1-H或1-H₂O。核磁共振研究表明这两个反应都具有显著的可逆性。因此，当暴露于H₂时，即使溶液中存在多当量的水，1-H₂O也会部分转化为1-H。向1中添加仲氢会在干燥和含水溶剂中导致核自旋超极化，证实了1-H₂O分解为游离的1。这些观察结果得到了计算研究的支持，表明由1形成1-H和1-H₂O在热力学上是有利的。出乎意料的是，1-H₂O可以释放分子氢形成氧化膦1-O。动力学、机理和计算(DFT)研究被用于阐明独特的“极性反转”水还原机制。
