Complex Carboranes as Weakly Coordinating yet Functional Anions

在这个项目中，由化学部的化学结构，动力学机制B计划资助，加州大学河滨分校化学系的Vincent Lavallo教授正在开发具有有趣特性的新类型离子化合物。 离子材料是盐。 Lavallo教授正在开发新型离子材料，其中带负电荷的部分（阴离子）和带正电荷的部分（阳离子）形成新材料，这些新材料可能在从制药到催化到环境废物修复的行业中具有应用。该小组在指导代表性不足群体的高中生方面有着悠久的历史，并将继续和扩大这些外联活动。 此外，本科生和研究生研究人员将直接参与该项目，并为他们提供培训，使他们为进入高科技领域的劳动力做好准备。弱配位阴离子通常起着旁观者的作用，在化学反应中几乎没有功能。 在这个项目中，实施超大体积的膦和N-杂环卡宾（NHC），含有两个共价键合的多卤代封闭碳硼烷阴离子，将探索作为弱配位阴离子，也能够控制反应性。 侧接膦和NHC孤对电子的旁观者碳硼烷在这些反应性位点处提供动力学保护，使得能够形成含有反应性阳离子和阴离子的复合离子对。这些系统类似于传统的受抑刘易斯对（FLP），除了这些物种是静电束缚。这些物质可以实现更具有挑战性的C-F键活化/基团转移，例如CF 4（一种有效的温室气体）的CF键断裂。此外，这些系统将提供一个独特的机会，以隔离所谓的难以捉摸的遭遇复杂的FLP化学。 这些系统将通过结晶离子对的固态氢化形成，并通过随后的低温微电子衍射分析进行研究。该项目的第二个实施方案是探索配体对由双阴离子膦和NHC负载的阴离子Au（I）加氢胺化催化剂的影响。这些过渡金属阴离子将与三苯甲基和甲硅烷基离子配对以形成能够在金属的配位层中产生高度反应性碳阳离子的试剂。 这种反应可能导致异裂氧化加成和前所未有的低配位烷基/芳基Au（III）化合物。靶向的Au（III）化合物将具有两个顺式可接近的配位位点，因此能够进行经典的d8过渡金属催化。这些物种介导迁移插入、羰基化以及其他低配位D8金属介导的其他反应的能力将被探索。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Vincent Lavallo of the Department of Chemistry at the University of California-Riverside is developing new classes of ionic compounds with interesting properties. An ionic material is a salt. Professor Lavallo is developing novel ionic materials where both the negatively charged part (anion) and the positively charged (cationic) portion form new materials that may have applications in industries ranging from pharmaceuticals to catalysis to environmental waste remediation. This group has a long history of mentoring high school students from underrepresented groups and will continue and expand these outreach activities. In addition, undergraduate and graduate student researchers will be directly involved in the project and provided with training to prepare them for entry into the workforce in high technology areas.Weakly coordinating anions generally function as spectators with little or no function in chemical reactions. In this project, the implementation of super bulky phosphines and N-Heterocyclic Carbenes (NHC), containing two covalently bound polyhalogenated closo-carborane anions, will be explored as weakly coordinating anions that are also capable of controlled reactivity. The spectator carboranes that flank the phosphine and NHC lone pairs of electrons provide kinetic protection at these reactive sites, enabling the formation of complex ion pairs that contain both a reactive cation and anion. These systems are akin to traditional frustrated Lewis pairs (FLP), except that these species are electrostatically tethered. Such species could achieve more challenging bond activations/group transfers for C-F bond activations, exemplified by the CF bond scission of CF4, a potent greenhouse gas. Additionally, these systems will provide a unique opportunity to isolate the so-called elusive encounter complex in FLP chemistry. These systems will be formed via the solid state hydrogenation of crystalline ion pairs and studied via subsequent analysis via cryo micro electron diffraction. A second embodiment of this project is the exploration of ligand effects on anionic Au(I) hydroamination catalysts, supported by the dianionic phosphines and NHCs. These transition metal anions will be paired with trityl and silylium ions to form reagents capable of generating highly reactive carbocations in the coordination sphere of the metal. Such reactions may lead to a heterolytic oxidative addition and unprecedented low-coordinate alkyl/aryl Au(III) compounds. The targeted Au(III) compounds will have two cis accessible coordination sites and thus may be capable of classical d8 transition metal catalysis. The ability of these species to mediate migratory insertion, carbonylations, as well as other reactions mediated by other low-coordinate D8 metals will be explored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.