Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstr. 40, 48149 Münster, Germany.
J Am Chem Soc. 2013 Jun 19;135(24):8882-95. doi: 10.1021/ja400338e. Epub 2013 Jun 7.
Hydroboration of dimesitylnorbornenylphosphane with Piers' borane [HB(C6F5)2] gave the frustrated Lewis pair (FLP) 4 in good yield. It has the -PMes2 Lewis base attached at the 2-endo position and the -B(C6F5)2 group 3-exo oriented at the norbornane framework. The vicinal FLP 4 was shown by X-ray diffraction and by spectroscopy to be a rare example of an intramolecular noninteracting pair of a Lewis acid and Lewis base functionality. The FLP 4 rapidly splits dihydrogen heterolytically at ambient temperature to yield the phosphonium/hydrido borate zwitterion 5. It adds to the carbonyl group of benzaldehyde and to carbon dioxide to yield the adducts 6 and 7, respectively. Compounds 5-7 were characterized by X-ray diffraction. Compound 4 adds to the S═O function of sulfur dioxide to give a pair of diastereomeric heterocyclic six-membered ring products due to the newly formed sulfur chirality center, annulated with the norbornane skeleton, which were investigated by (31)P/(11)B single and double resonance solid state NMR experiments. Compound 8 was also characterized by X-ray diffraction. The FLP 4 undergoes a clean N,N-addition to nitric oxide (NO) to give a norbornane annulated five-membered heterocyclic persistent FLP-NO aminoxyl radical 12 (characterized, e.g., by X-ray diffraction and EPR spectroscopy). Additionally, the FLP radical was characterized by (1)H solid state NMR spectroscopy. The radical 12 undergoes a H-atom abstraction reaction with 1,4-cyclohexadiene to yield the respective diamagnetic FLP-NOH product 13, which was also characterized by X-ray diffraction and solid state NMR spectroscopy.
二甲基亚芳基降冰片烯膦与皮尔斯硼烷[HB(C6F5)2]的硼氢化反应以良好的收率得到受阻路易斯对（FLP）4。它具有 -PMes2 路易斯碱，连接在 2-endo 位置，-B(C6F5)2 基团 3-exo 定向在降冰片烷骨架上。通过 X 射线衍射和光谱学证明，顺式 FLP 4 是路易斯酸和路易斯碱功能的分子内非相互作用对的罕见实例。FLP 4 在环境温度下迅速异裂分解氢气，生成磷翁/氢硼酸酯两性离子 5。它加成到苯甲醛的羰基和二氧化碳上，分别生成加合物 6 和 7。化合物 5-7 通过 X 射线衍射进行了表征。化合物 4 加成到二氧化硫的 S═O 官能团上，由于新形成的硫手性中心，与降冰片烷骨架环合，生成一对非对映异构的杂六元环产物，这对产物通过（31）P/（11）B 单和双共振固态 NMR 实验进行了研究。化合物 8 也通过 X 射线衍射进行了表征。FLP 4 与一氧化氮（NO）发生干净的 N，N-加成反应，生成一个环合有降冰片烷骨架的五元杂环持久性 FLP-NO 氮氧自由基 12（例如通过 X 射线衍射和 EPR 光谱学进行了表征）。此外，自由基 12 通过（1）H 固态 NMR 光谱学进行了表征。自由基 12 与 1,4-环己二烯发生 H-原子抽取代反应，生成相应的抗磁性 FLP-NOH 产物 13，该产物也通过 X 射线衍射和固态 NMR 光谱学进行了表征。
