CAS: Can the Ionic Character of 1st Row and the Covalency of 2nd and 3rd Row Transition Metals Converge?

普通公众摘要：国家科学基金会化学部化学合成计划支持康奈尔大学Peter T.Wolczanski教授的研究。该项目旨在培训以金属为中心的化学领域的候选人。大多数商品(散装)和精细(药用)化学品都是利用催化剂合成的。这些催化剂通常是过渡金属化合物，可以加快反应速度。其中许多催化剂使用的金属丰度低、有毒且价格昂贵。该项目正在研究更便宜的催化剂的合成，但它们必须用有机材料--称为配体--进行修饰，以便提供必要的化学反应能力，以取代工业上使用的当前一代催化剂。一个正在探索的普遍解决方案是研究有望使更便宜的金属更具多功能性或适应性的配体。另一种普遍的方法是合成金属体系，这将支持真正的转变过程：制备能够进行多步化学反应的化合物。一种特定的应用是利用螺旋桨状分子断裂生成所谓的亚烷基配体来合成络合物。亚烷基金属化合物的合成将对美国化学工业中的先进制造产生广泛的影响。康奈尔大学的组织还支持五年级和高中生的STEM教育。STEM的工作包括授课材料和实践培训模块。这些活动有助于加强可用于支持美国化学工业的劳动力。技术摘要：国家科学基金会化学部化学合成计划支持康奈尔大学Peter T.Wolczanski教授的研究计划。该项目旨在培养无机和有机金属化学领域的博士生。这项研究确定了在商品(散装)和精细(药用)化学品生产方面具有潜在变革性的几种反应。用于催化的典型过渡金属丰度低且价格昂贵，这项工作建议用廉价的第一排和第二排物种取代这些物种。各种显示氧化还原非无辜的配体平台，包括可逆的C-C键的形成，被用来扩展几个第一排金属的氧化还原能力。其他三配位络合物也参与了氢转移化学，以进一步扩大反应范围。探索离子对共价键是这项工作的基础。转移HX和H2加成，类似于转移氢化，以及氢甲酰化等过程，是早期金属系统的目标。特定的体系显示出串联CH活化与烯烃歧化结合的潜力，导致H2与CH2的净交换，并且一个三齿配体具有替代Ziegler-Natta聚合机制的潜力。独特的应变试剂被用作许多过渡金属的亚烷基催化剂，因为取代昂贵的Ru基烯烃歧化催化剂是一个重要的目标。培养能够适应充满挑战和波动的学术或工业市场的独立、多才多艺的博士是一个主要目标，作为正式氧化态的教学替代方案的电荷分布(CDVR)的进一步发展将继续受到测试。康奈尔大学的团队还在根据经验准备一个普通的五年级推广计划，并正在为高中生开发一个相关的推广计划。这个奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

General Public Abstract:The Chemical Synthesis Program of the Chemistry Division of the National Science Foundation supports the research of Professor Peter T. Wolczanski of Cornell University. The project seeks to train candidates in the fields of metal-centered chemistry. Most commodity (bulk) and fine (pharmacological) chemicals are synthesized utilizing catalysts. These catalysts are typically transition metal compounds that accelerate the rates of reaction. Many of these catalysts use metals that are in low abundance, toxic, and expensive. This program is studying the synthesis of cheaper catalysts, but they must be modified by organic materials -- termed ligands -- in order to provide the chemical reactivity necessary to replace the current generation of catalysts used in industry. One general solution being explored is the investigation of ligands that promise to render the cheaper metals more versatile or adaptable. Another general approach is to synthesize metal systems that will underpin truly transformative processes: the preparation of compounds that are capable of multistep chemical reactions. A specific application targets the synthesis of complexes using propellar-shaped molecules that rupture to give what are called alkylidene ligands. Synthesis of alkylidene-metal compounds would have broad implications for the advanced manufacturing within the U.S. chemical industry. The Cornell group is also supports STEM education of 5th grade and high school students. The STEM efforts include lecture materials and hands-on training modules. These activities are helping to strengthen the workforce available to support the US chemical industry.Technical Abstract:The Chemical Synthesis Program of the Chemistry Division of the National Science Foundation supports the research program of Professor Peter T. Wolczanski of Cornell University. The project seeks to train PhD candidates in the fields of inorganic and organometallic chemistry. The research identifies several reactions that are potentially transformative in regards to commodity (bulk) and fine (pharmacological) chemicals production. Typical transition metals used in catalysis are in low abundance and costly, and the work proposes to supplant these species with inexpensive 1st and 2nd row species. Various ligand platforms that display redox non-innocence, including a reversible C-C bond formation, are employed to expand the redox capacity of several first-row metals. Other 3- coordinate chelates are also involved in H-transfer chemistry to further expand the scope of reactivity. Exploration of ionic vs. covalent bonding is fundamental to the work. Transfer HX and H2 additions, akin to transfer hydrogenations, and processes like hydroformylation, are targeted with early metal systems. Specific systems show potential for tandem CH activation in conjunction with olefin metathesis, leading to a net exchange of H2 for CH2, and one tridentate ligand has the potential for an alternate polymerization mechanism to Ziegler-Natta. Unique strained reagents are employed as alkylidene generators for numerous transition metals, as replacing expensive Ru-based olefin metathesis catalysts is an important target. The production of independent, versatile PhDs capable of adapting to a challenging and fluctuating academic or industrial market is a major objective, and the further development of Charge Distribution Via Reporters (CDVR) as a pedagogical alternative to formal oxidation states will continue to be tested. The Cornell group is also preparing a general 5th grade outreach program for publication based on experience, and is developing a related outreach program for high school students.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.