Selective Catalysts with an Inward Facing N-Heterocyclic Carbene

化学催化项目支持由纽约州立大学布法罗分校的Steven T. Diver教授领导的合成一种新的大环n杂环碳的研究。这种独特的大循环设计特点是一个多功能配体指向分子腔的内部。n-杂环碳烯是一种强大的亲核试剂，对催化碳-碳键的形成和钌等过渡金属的配体都很有用。大环配体的设计是为了将过渡金属牢牢地保持在其内部，在那里选择性的烯烃复分解反应发生。目前的碳钌催化剂表现出较高的化学选择性（对烯烃的偏好），但本研究解决了它们的一些主要缺点，包括分解、关键催化中间体的寿命和选择性。预计大环的限制性质将限制分解途径，并将显示其化学反应物的尺寸选择性，这是烯烃复分解反应中未知类型的选择性。烯烃复分解是合成小分子、材料和能源应用的重要反应，在大规模工业应用、药物合成和药物化学中用于药物发现。在美国国家科学基金会化学分部化学催化项目的支持下，Steven T. Diver教授和他的研究团队基于占据腔内的金属，获得了具有广泛应用的新型化学催化剂。在这种受控环境下研究了强亲核配体的基本性质。新型碳钌催化剂的研究有望为可持续能源领域提供更耐用的催化剂。例如，高寿命的碳钌催化剂对于生产经济上可行的生物柴油燃料至关重要。外联部分旨在通过高中生的催化项目和K-12学生的化学荣誉徽章日，依靠高中生和研究生领导活动，提高青年对化学作为实验科学的认识。动力学实验是说明如何通过实验控制自然现象和如何呈现数据的理想方法。人们需要活性更高、寿命更长、选择性更高的催化剂，而本研究项目中研究的烷烃复分解反应被用作制造化学生物学探针和染料的工具。钌羰基包封是通过限制双分子分解来控制催化剂选择性和提高催化剂稳定性的新途径。这一概念可能被证明广泛适用于其他金属催化应用。

The Chemical Catalysis Program supports research led by Professor Steven T. Diver at the State University of New York (SUNY) at Buffalo on the synthesis of a new macrocyclic N-heterocyclic carbene. This unique macrocycle design features a versatile ligand pointing inward toward the inside of the molecular cavity. N-Heterocyclic carbenes are powerful nucleophiles useful both for catalytic carbon-carbon bond formation and as ligands for transition metals such as ruthenium. The macrocyclic ligand is designed to hold transition metals firmly in its interior where selective alkene metathesis reactions take place. Current ruthenium carbene catalysts display high chemoselectivity (preference for alkenes), but some of their key shortcomings are addressed by this research, including decomposition, lifetime of a key catalytic intermediate, and selectivity. The restrictive nature of the macrocycle is expected to limit decomposition pathways and will display size selectivity for its chemical reactants, an unknown type of selectivity in the alkene metathesis reaction. Alkene metathesis is an important reaction for the synthesis of small molecules, materials, and for energy applications and is used in large-scale industrial applications, the synthesis of pharmaceuticals, and in medicinal chemistry for drug discovery.With the support of the Chemical Catalysis Program in the Chemistry Division at the National Science Foundation, Professor Steven T. Diver and his research team access new chemical catalysts with a wide range of applications based on the metal occupying the interior of the cavity. Fundamental properties of the strong nucleophilic ligand are investigated in this controlled environment. The investigation of new ruthenium carbene catalysts is expected to produce more durable catalysts for applications in sustainable energy. For example, higher lifetime ruthenium carbene catalysts are critical in producing biodiesel fuel that are economically-viable. The outreach component seeks to increase awareness of chemistry as an experimental science to youth through a catalysis project for high school students and for K-12 students through a chemistry merit badge day, relying on high school students and graduate students to lead activities. Kinetics experiments are ideal to illustrate how natural phenomenon can be controlled through experiment and how data can be presented. Catalysts that display increased activities, longer lifetimes, and higher selectivities are in demand and alkane metathesis, the reaction under scrutiny in this research project, is used as a tool to make probes and dyes for chemical biology. Encapsulation of ruthenium carbenes represents a new approach to controlling selectivity and improving stability of a catalyst by limiting bimolecular decomposition. This concept may prove broadly useful to other metal-catalyzed applications.