In this project funded by the Chemical Synthesis Program of the Chemistry Division, Professor Peter T. Wolczanski of the Department of Chemistry and Chemical Biology at Cornell University will explore the utilization of first row transition metals in new carbon-carbon bond forming reactions, selective dinitrogen binding reactions, the oxidative functionalization of hydrocarbons, and metal clusters as potential water reduction catalysts. Radical reactions are one means to oxidize hydrocarbons, but the lack of selectivity in these transformations limits their utility. The research proposed suggests a way of controlling radical processes that will permit selective oxidations to be performed. Furthermore, dihydrogen (H2) that is not produced from hydrocarbons (its predominant source) is a promising alternative fuel, and this research explores different approaches to water reduction as a means to produce H2.
In terms of broader impacts, the proposed work could lead to new C-C bond forming processes that can be applied to the synthesis of commodity or fine (e.g., drugs) chemicals. Hydrocarbon oxidation and water splitting are critical synthesis and energy problems of the 21st century. The direct transformation of hydrocarbons to value-added products has the potential for enormous energy and cost savings. Graduate and undergraduate students will be trained in various spectroscopies, X-ray crystallography, kinetics and mechanistic evaluations, molecular orbital calculations as well as in handling air sensitive compounds. Dissemination of this research through presentations at meetings, and via the promotion of science at the 5th-grade level and to 8th grade girls, is included. The production of independent, versatile PhDs capable of adapting to a challenging and fluctuating postdoctoral, academic or industrial market is a concurrent human resource objective.
(CHE-1055505, 8/1/11-7/31/14). For the layperson, the titles of scientific programs can often be incomprehensible, sometimes intimidating, and even mysterious, but the goals are actually quite general. NSF support in the academic community has two integrated targets: 1) the education and training of PhD candidates, undergraduates (UG), and postdoctoral fellows (PD); and 2) research. Inclusive to both is the dissemination of scientific discoveries and information to the general public in appropriate forums. While those forums - typically journal publications and American Chemical Society meetings -- may seem narrow in focus and targeted toward other professionals, they are nonetheless accessible. The educational and research missions entail broader and intellectual, i.e. research, impacts as mandated by the NSF. In this project, five graduate students (GS) received financial support, and four have obtained PhDs: Prof. Elliott B. Hulley is starting his independent research career at the Univ. of Wyoming after a postdoctoral stint at Pacific Northwest National Laboratory; Dr. Erika R. Bartholomew is a staff scientist at Merck Pharmaceuticals, and Dr. Valerie A. Williams and Dr. Wesley D. Morris are in their first year of postdoctoral studies. Brian M. Lindley is scheduled to obtain his PhD in 8/2015. Undergraduates Martin Roskoff (GS, Univ. Washington), Rishi Aggarwal, and Nick Livesay were also partly supported by the grant. The graduate students presented their research at the 2011, 2012, 2013 and 2014 Organometallic Gordon Research Conferences, the premier yearly meeting for this field. Research seminars were given by PTW at the 2011, 2012, 2013, and 2014 spring American Chemical Society meetings. For local outreach, the group continued its affiliation with Caroline Elementary School (Ithaca, NY), where it ran a spring Chemistry Club (5th grade) for the second consecutive funding period, participated in Expanding Your Horizons, a campus-wide day of experimentation targeting junior high and HS girls, and hosted a half-time an Ithaca high school summer student. This proposal was funded by Chemical Synthesis and addresses the following scientific national need. Molecules are often synthesized using transition metal complexes -- metals surrounded by other atoms or groups of atoms termed ligands -- as entities help convert raw materials to end products: commodity and fine chemicals. The transition metals that catalytically conduct these transformations are mostly found in the 4th and 5th periods of the periodic table, i.e. the second and third row of the transition elements. These elements are expensive, often toxic, and their supply is dwindling. In contrast, 1st row transition elements are abundant, largely less toxic, and are cheap. The proposal goals were: 1) to expand the scope of 1st row transition metal complexes that express redox non-innocence (RNI), and 2) prepare new species capable of unique C-C bond-forming processes. The intent is to generate transformative chemistry by changing the way metal-ligand interactions are viewed, and to ultimately employ such species as replacements of current 2nd row complexes. Ligands that have the property of redox non-innocence can expand the capabilities of 1st row transition metals, and roughly 100 new compounds were synthesized and investigated in this context. While the goal of achieving catalysis was not reached, the basis of an electronic understanding of redox non-innocence (RNI) was founded. The ideas will be tested in the ensuing grant period, since a continuing goal is to uncover how redox non-innocence can be used to foment chemical reactivity at the metal and the ligand. Ligand designs featuring redox non-innocence were instrumental in the discovery of single and multiple C-C bond formations. Transformations of this type are intriguing, and represent a potentially transformative approach to fine chemicals, while RNI can be a stabilizing property of N-donor chelates in certain instances. Through synthesis of specific chelate complexes of iron, complexes that selectively extract N2 from air were discovered, and complementary calculational studies permitted an understanding of how the process occurs. Practical application of these concepts to N2 removal from hydrocarbon feed streams is a possibility, and strong ligation affiliated with M-C bonds provides a rationale for why a carbon atom is central to the operation of the nitrogenase enzyme. Prior CH-bond activation research was elaborated to include studies of alkane binding, and ligand-induced H2 and cyclometallation events that circumvent the constraints of orbital symmetry were also completed. In summary the project met its human resource goals, and the intellectual goals of providing an understanding of redox non-innocence in its application to first row transition metal complexes.
