Strongly Electrophilic Borenium Ions for Small Molecule Activation

强亲电性硼离子的化学性质是目前研究的热点。表现出B-H功能的反应性硼离子是罕见的。麻省理工大学的Erker小组最近开发了一种方便的合成方法来合成n -杂环碳稳定的B-H硼离子体系。我们将开发一系列这样的硼化合物，除了在硼上含有强吸电子的ArF氟芳基取代基[ArF =五氟苯基，3,5-二（三氟甲基）苯基（Fxyl）或2,4,6-三（三氟甲基）苯基（Fmes）]外，还含有n-杂环卡宾（NHC）或环烷基氨基卡宾（CAAC）配体]。我们将首先确定这种体系在各种典型的B-H反应中的具体反应活性。然后，我们将使用强亲电性的B-H硼来生成高级受挫刘易斯对（FLPs）。这些将应用于当前化学计量和催化加氢过程的发展。这将涉及一氧化碳和二氮还原的新途径，以及烯烃、炔和杂环转化的活性催化剂的发展。新的FLPs将被测试其在C-H活化过程中的能力。我们想研究B-H硼离子的去质子化是否可能为生成反应性NHC/CAAC稳定的硼炔开辟一条便利的途径。最终，我们想尝试用烷基硼离子的脱质子路线制备中性[NHC/CAAC]B(ArF)=CHR体系，以寻找无金属烯烃和乙炔的复分解路线。

The chemistry of strongly electrophilic borocations is of high current interest. Reactive borenium ions that exhibit a B-H functionality are rare. The Erker group at Münster has recently developed a convenient synthetic route to N-heterocyclic carbene-stabilized B-H borenium ion systems. We will develop a series of such boron compounds that contain N-heterocyclic carbene (NHC) or cyclic alkylamino carbene (CAAC) ligands in addition to a strongly electron-withdrawing ArF fluoroaryl substituent [ArF = pentafluorophenyl, 3,5-bis(trifluoromethyl)phenyl (Fxyl) or 2,4,6-tris(trifluoromethyl)phenyl (Fmes)] at boron. We will first determine the specific reactivities of such systems in a variety of typical B-H reactions. We will then use the strongly electrophilic B-H boreniums for the generation of advanced frustrated Lewis pairs (FLPs). These shall be employed in the current development of stoichiometric and catalytic hydrogenation processes. That shall involve novel pathways in carbon monoxide and dinitrogen reduction and in the development of active catalysts for alkene, alkyne and heterocycle conversions. The new FLPs shall be tested for their ability in C-H activation processes. We want to investigate if deprotonation of our B-H borenium cations might open a convenient route to generating reactive NHC/CAAC stabilized borylenes. Eventually we want to try making neutral [NHC/CAAC]B(ArF)=CHR systems by deprotonation routes from our alkyl borenium cations in a search for metal-free olefin and acetylene metathesis routes.