CAS: Can 1st Row Transition Metals Express the Covalency Typifying 2nd and 3rd Row Transition Metals: Comparative Studies

CAS：第一行过渡金属能否表达代表第二行和第三行过渡金属的共价：比较研究

• 批准号: 2348673
• 负责人: Peter Wolczanski
• 金额: $ 57.5万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-08-01 至 2027-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2348673&HistoricalAwards=false
• 关键词: CAS; 1st; Row; Transition; Metals

With the support of the Chemical Synthesis Program of the Chemistry Division, Professor Peter T. Wolczanski and his research team at Cornell University will investigate whether 1st row transition metals can be induced to express covalency typical of 2nd and 3rd row metals. Most commodity and fine chemicals are synthesized utilizing catalytic chemistry, with 2nd row transition metals being used to catalyze bond formations to carbon most commonly. Many of these metals are in low abundance and expensive; so-called precious metals. This research is directed at developing more sustainable alternative chemistries; namely by establishing ways of utilizing more abundant metals that are modified by ligands to provide the chemical reactivity necessary to supplant the current catalysts. Transformative ligands that expand the scope of applications via unique reactivity are a cornerstone of the program. A number of approaches involving different metal-ligand binding modes, and different electronic capabilities are expected to allow for the effective modulation of catalyst reactivity. One specific application is the synthesis of simple coordination complexes to enable light-initiated processes to occur more sustainably and with greater facility. An internet program/website will be established to provide a forum for Q&A for the community, and to serve as a news interface with the general public. The project will train graduate and undergraduate students in the fields of inorganic and organometallic chemistry in the synthesis and reactivity of transition metal compounds. As an ancillary effort an oral history organometallic chemistry will be assembled and made accessible through the internet.The coordination of strong field and redox non-innocent (RNI) ligands will be utilized with the goal of expanding the redox capability of targeted 1st transition series metals. The goal is the development of catalytic properties of these metals that are typical of 2nd and 3rd row metals. As strong fields impart covalency, bidentate pyrimidine-based chelates featuring anionic or neutral M-C bonds will be employed as inductively withdrawing ligands. As these complexes are predicted to have low-lying pi-antibonding orbitals and corresponding low-lying charge-transfer (CT) excited states, the complexes have potential applications as photoactive materials in photocatalysis. Reversible C-C bond breaking will be employed in low coordinate complexes to restrict RNI to 2e- changes. Chromium tetradentate chelates manifest chemistry that provides proof of this concept. New chelates with sterically/electronically protected components will hamper degradation and stabilize ligand platforms that will enable CH activation through transient imide/nitrene complexation. Non-ancillary ligands based on benzimidazole diamides will be used to reversibly mask alkylidenes that are capable of ring-opening metathesis polymerization and olefin metathesis. Using this ligand system, a reversible cycle involving a net methylene/dihydrogen metathesis will be realized. Additional fundamental information will be gleaned from comparisons of Cr vs Mo or W, Ti vs Zr, or V vs Nb, where comparative chemistry (metalaradical vs concerted) will elicit interpretations based on covalency.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.

在化学系化学合成项目的支持下，Peter T. Wolczanski和他在康奈尔大学的研究小组将研究是否可以诱导第一行过渡金属表达第二和第三行金属的典型共价。大多数商品和精细化学品都是利用催化化学合成的，第二行过渡金属通常用于催化碳的键形成。这些金属中有许多是低丰度和昂贵的;所谓的贵金属。这项研究旨在开发更可持续的替代化学品;即通过建立利用更丰富的金属的方法，这些金属被配体修饰，以提供取代当前催化剂所需的化学反应性。通过独特的反应性扩大应用范围的转化配体是该计划的基石。许多涉及不同金属-配体结合模式和不同电子能力的方法预期允许催化剂反应性的有效调节。一个具体的应用是合成简单的配位络合物，使光引发的过程更可持续地发生，并具有更大的设施。将建立一个互联网程序/网站，为社区提供一个问答论坛，并作为与公众的新闻界面。该项目将在过渡金属化合物的合成和反应性方面对无机和有机金属化学领域的研究生和本科生进行培训。作为一个辅助的努力，有机金属化学的口述历史将通过互联网组装和访问。强场和氧化还原非无辜（RNI）配体的配位将被利用，目标是扩大目标第一过渡系列金属的氧化还原能力。目标是开发这些金属的催化性能，这些金属是第二和第三行金属的典型特征。由于强电场赋予共价性，因此将采用以阴离子或中性M-C键为特征的基于嘧啶的二齿螯合物作为感应吸走配体。由于这些配合物具有低π-反键轨道和相应的低电荷转移（CT）激发态，因此具有作为光活性材料的潜在应用价值。在低配位络合物中将采用可逆的C-C键断裂以将RNI限制为2 e-变化。铬四齿螯合物的化学性质为这一概念提供了证据。具有空间/电子保护组件的新螯合物将阻碍降解并稳定配体平台，这将使CH通过瞬时酰亚胺/氮烯络合活化。基于苯并咪唑二酰胺的非辅助配体将用于可逆地掩蔽能够开环易位聚合和烯烃易位的亚烷基。使用该配体系统，将实现涉及净亚甲基/二氢复分解的可逆循环。通过比较Cr与Mo或W、Ti与Zr或V与Nb，将收集更多的基本信息，其中比较化学（金属基与协同）将根据共价性进行解释。该奖项反映了NSF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。