Bonding and Reactivity in Low-Valent Dinickel Complexes

低价二镍络合物的成键和反应性镍化合物的一个显著特性是它们具有破坏强化学键的能力。事实上，一些蛋白质含有镍中心，可以与二氧化碳发生反应，两者之间的化学键非常强。镍基催化剂广泛应用于能源相关化学领域。乔治亚理工学院（Georgia Institute of Technology）的约瑟夫·p·萨迪吉（Joseph P. Sadighi）教授领导的研究项目建立在这些强化学键和能源相关性的主题之上。该项目的重点是镍原子对。镍原子通过桥接原子或桥接基团成对连接。在这项工作中探索的连接物包括氢、非金属元素或其他金属。该项目检查与每个镍中心弱结合的桥接中心。这些异常弱的键会使配合物足够稳定，可以被分离，但又不稳定，足以产生高活性。对这些化合物的更深入了解将为设计破坏强键的催化剂提供洞见。进行这项研究的研究生和本科生研究人员被介绍了键和反应性的概念，以及一系列合成和光谱技术。该组织还参与了乔治亚理工学院（Georgia Tech）的一个项目，该项目旨在从科学领域代表性不足的人群中招募高中生。学生们会在整个夏季和整个学年中进行研究。这种培训使学生能够作为教师，或作为学术、工业或政府实验室的研究人员，为美国科学的未来做出贡献。PI与正在服役或最近转业的退伍军人有广泛的联系，并为那些重返全日制学习的退伍军人提供建议和鼓励。近年来，镍在金属元素键合、断键和成键等催化反应方面取得了显著进展。本研究提出了两个镍(0)中心与路易斯酸相互作用形成桥接配体的结构。当路易斯酸是质子时，这种相互作用产生了罕见的线性氢化物桥；[Ni—H—Ni]+核由一个三中心、四个电子的键连接在一起，类似于二氟离子。一个目的是合成一系列相关的氢化物桥接的二镍配合物，从而能够评估桥接氢的水合性质，并详细研究配合物对腈的C-CN键的反应性。另一个目的是探索由刘易斯酸性主基团形成的桥，如碳阳离子、硼烷、烷烃或有机金属碎片。最后，在镍中心之间插入铜(I)或金(I)阳离子将使异质金属体系具有跨越三个金属中心的单一净键。支持这些目标的假设是，[Ni-E -Ni]系综足够稳定，可以分离或表征，但其反应性与单镍配合物[Ni-E]、单独的镍或单独的桥接元素不同。参与该项目的学生将学习键合和化学合成的概念。他们获得了制备空气敏感复合物的技术技能。他们接受过使用现代仪器进行分析的训练。这些研究人员包括研究生、本科生和高中生。该项目旨在识别对科学研究感兴趣的少数族裔学生。这项培训为学生在教育、研究和工业领域的技术职业做好准备。在另一种形式的拓展中，萨迪吉教授建议退伍军人重返全日制学习。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Bonding and Reactivity in Low-Valent Dinickel ComplexesA remarkable property of nickel compounds is their ability to break strong chemical bonds. Indeed, some proteins contain nickel centers that react with carbon dioxide, which has very strong bonds. Catalysts based on nickel are widely used in energy-related chemistry. The research project led by Professor Joseph P. Sadighi at the Georgia Institute of Technology builds on these themes of strong bonds and energy-relevance. The project focuses on pairs of nickel atoms. The nickel atoms are linked in pairs using bridging atoms or bridging groups. The linkers that are explored in this work include hydrogen, nonmetallic elements, or another metal. The project examines bridging centers that are weakly bonded to each nickel center. These unusually weak bonds should make the complexes sufficiently stable to be isolated, yet unstable enough to be highly reactive. A deeper understanding of these compounds is providing insights into the design of catalysts for breaking strong bonds. The graduate and undergraduate researchers who carry out this research are introduced to concepts of bonding and reactivity, and to an array of synthetic and spectroscopic techniques. The group also participates in a Georgia Tech program to recruit high school students from demographics underrepresented in science. The students are introduced to research through a summer and then through the academic year. This training prepares students to contribute to the future of science in the United States as teachers, or as researchers in academic, industrial, or government laboratories. The PI has extensive contacts with currently serving or recently transitioned veterans, and provides advice and encouragement to those returning to full-time study.Nickel has been the subject of remarkable recent advances in metal-element bonding, and in bond-breaking and bond-forming reactions that enable catalysis. This research presents architectures derived from the interaction of two nickel(0) centers with a Lewis acid to form a bridging ligand. When the Lewis acid is a proton, this interaction creates a rare linear hydride bridge; The [Ni---H---Ni]+ core is held together by a three-center, four-electron bond, analogous to that in the bifluoride ion. One aim is the synthesis of a series of related hydride-bridged dinickel complexes, enabling an assessment of the hydridic character of the bridging hydrogen, and a detailed study of the complex's reactivity toward the C-CN bonds of nitriles. Another aim explores the formation of bridges derived from Lewis-acidic main group species such as carbocations, boranes, alanes, or organometallic fragments. Finally, the insertion of copper(I) or gold(I) cations between the nickel centers would afford heterometallic systems with a single net bond across three metal centers. The hypothesis underpinning these aims is that the [Ni---E---Ni] ensembles are sufficiently stable for isolation or characterization, yet display reactivity distinct from that of mononickel complexes [Ni-E], nickel alone, or the bridging element alone. Students who work on this project learn concepts of bonding and chemical synthesis. They acquire technical skills in the preparation of air-sensitive complexes. They are trained in analysis using modern instrumentation. These researchers include graduate students, undergraduates, and high school students. The program identifies underrepresented minority students interested in scientific research. This training prepares students for technical careers in education, research, and industry. In another form of outreach, Professor Sadighi advises fellow veterans on their return to full-time study.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.