Synthetic Manipulation of Main Group Elements with Transition Metal Isocyanides

在化学系化学合成计划的支持下，加州大学圣地亚哥分校的Joshua S.Figueroa教授将研究以异氰化物为支撑基的过渡金属化合物如何控制和调节主族元素的化学和行为。本项目中使用的异氰化物支撑基为过渡金属和主族元素之间的化学相互作用提供了保护。反过来，这种屏蔽又允许制备和分离通常不稳定和难以获得的分子。该奖项的一个特别重点是使用铁异氰化物来研究和了解双原子分子一氟化硼(BF)和双磷的基本性质和化学反应活性。一氟化硼作为一种自由分子，由于极端的成键极化，在环境条件下不稳定。同样，与其较轻的类似氮不同，二磷在正常条件下也不是一个稳定的分子，而是更喜欢凝聚成多磷固体材料。随着间三苯基异氰酸酯支撑基的出现，合成了同时含有BF和二磷的稳定分子。在这一裁决过程中，将对高炉和双磷的基本性质进行详细的调查。这些研究试图提供基本问题的答案，包括1)金属结合的BF和双磷如何与其他分子反应，2)BF和双磷如何影响它们所结合的金属上的化学行为，以及3)与自由但不稳定的分子相比，金属结合的BF和双磷的反应性如何？该项目还将侧重于其他过渡金属支持的主族元素物种的制备和表征，特别强调产生其他不寻常或未知的双原子分子。更广泛的影响活动将包括学生研究培训和指导，为即将入学的研究生开发动手实验室安全课程，以及对转学学生的指导。该项目将特别侧重于由过渡金属间三苯基异氰酸酯络合物稳定的不寻常主基碎片的合成和反应活性。根据最近披露的合成铁末端一氟化硼(BF)络合物和铁的单核双磷络合物的报道，将进行详细的研究，旨在阐明这些不寻常的双原子配体与外源底物的反应活性以及它们对它们所结合的过渡金属中心的具体影响。具体来说，对于终端BF络合物，将进行合成研究，旨在扩大硼中心显著的亲电性，同时详细说明导致BF单元在通往其他金属-硼络合物的途中发生裂解的反应轮廓。在单核双磷铁络合物的情况下，它的侧向结合模式为阐明磷和碳之间的基本周期对角关系提供了机会。因此，将进行反应性研究，目的是比较和对比金属稳定的双磷与乙炔和其他取代炔烃的反应性。具体到这些努力，将评估侧基配位双磷和有机双烯之间的Diels-Alder类型反应的范围。此外，根据初步证据，将评估侧基配位双磷与一系列亲核底物的亲电特性。在研究BF和与铁配位的二磷的性质的同时，还将制备和/或研究其他低价过渡金属间三苯基异氰酸酯配合物，以稳定不寻常的主基碎片的能力，重点是制备其他不稳定或未知的双原子分子，特别是较重的p-嵌段元素。另一个重点将放在其他过渡金属的BF络合物的合成上，以努力测试关于稳定这种反应性双原子分子所需的因素、电子环境(S)和条件的电子结构假说。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。

With the support of the Chemical Synthesis program in the Division of Chemistry, Professor Joshua S. Figueroa of the University of California, San Diego will study how the chemistry and behavior of main-group elements can be controlled and modulated by transition metal compounds featuring isocyanide supporting groups. The isocyanide supporting groups used in the context of this project provide a protective shield for the chemical interactions between the transition metal and main-group elements. This shield, in turn, allows for the preparation and isolation of molecules that are usually unstable and difficult to obtain. A specific focus of this award is to use iron isocyanide compounds to study and understand the fundamental properties and chemical reactivity of the diatomic molecules boron monofluoride (BF) and diphosphorus. Boron monofluoride, as a free molecule, is not stable under ambient conditions on account of the extreme bonding polarization. Similarly, diphosphorus, unlike its lighter analogue dinitrogen, is also not a stable molecule under normal conditions, preferring instead to condense into polyphosphorus solid materials. With the advent of the m-terphenyl isocyanide supporting groups, stable molecules containing both BF and diphosphorus have been prepared. In the course of this award, detailed investigations into the fundamental nature of BF and diphosphorus will be conducted. These investigations seek to provide answers to basic questions, including 1) how do metal-bound BF and diphosphorus react with other molecules, 2) how do BF and diphosphorus influence the chemical behavior on the metals to which they are bound and, 3) how does the reactivity of metal-bound BF and diphosphorus compare to that of the free, yet unstable, molecules? This project will also focus on the preparation and characterization of other transition-metal-supported main-group element species, with a specific emphasis on generating other unusual or unknown diatomic molecules. The broader impacts activities will include student research training and mentoring, the development of a hands-on laboratory safety course for incoming graduate students, and mentorship of transfer students.This project will specifically focus on the synthesis and reactivity of unusual main-group fragments stabilized by transition-metal m-terphenyl isocyanide complexes. Building on recent reports disclosing the synthesis of an iron terminal boron monofluoride (BF) complex, and a mononuclear diphosphorus complex of iron, detailed investigations will be conducted that aim to elucidate the reactivity of these unusual diatomic ligands with exogenous substrates as well as their specific influence on the transition metal centers to which they are bound. For the terminal BF complex specifically, synthetic studies will be conducted that aim to expand on the pronounced electrophilicity of the boron center, while at the same time detailing reaction profiles that result in the cleavage of the BF unit en route to other metal-boron complexes. In the case of the mononuclear diphosphorus iron complex, its side-on binding mode presents the opportunity to expound upon the fundamental periodic diagonal relationship between phosphorus and carbon. Accordingly, reactivity studies will be conducted that aim to compare and contrast the reactivity of metal-stabilized diphosphorus with that of acetylene and other substituted alkynes. Specific to these efforts will be an assessment of the scope of Diels-Alder-type reactivity between side-on coordinated diphosphorus and organic dienes. In addition, based on preliminary evidence, the electrophilic character of the side-on coordinated diphosphorus with a range of nucleophilic substrates will be evaluated. In parallel to investigations into the nature of BF and diphosphorus coordinated to iron, other low-valent transition metal m-terphenyl isocyanide complexes will be prepared and/or studied with respect to their ability to stabilize unusual main-group fragments, with a focus on the preparation of other unstable or unknown diatomic molecules, especially of the heavier p-block elements. An additional emphasis will be placed on the synthesis of BF complexes of other transition metals in an effort to test electronic structure hypotheses on the factors, electronic environment(s) and conditions that are required to stabilize this reactive diatomic molecule.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.