CAS-MNP: Dimetallic CO Homocoupling and Functionalization

University Of Florida, Gainesville FL

Investigators

Abstract

With funding from the Chemical Synthesis Program in the Chemistry Division, Leslie Murray of the Department of Chemistry at the University of Florida will investigate how iron compounds are able to facilitate the formation of new carbon-carbon bonds between carbon monoxide molecules. Carbon monoxide is a feedstock used by chemical industry to prepare many important products. The motivation for this study is to understand the details of a process (called the Fischer-Tropsch (FT) synthesis) that converts carbon monoxide into lubrication oils and fuels. While the FT synthesis has been known for nearly 100 years, some important details of how it functions are still unclear. In particular, the details of how two carbon monoxide molecules link together in the presence of iron atoms has not yet been established. This project will prepare a series of compounds that contain several iron atoms and that are capable of coupling carbon monoxide molecules. The detail of how this coupling occurs will be determined using both chemical and physical studies. In addition to the scientific objective, this project includes training of graduate and undergraduate students and outreach to K-12 students, including those from underrepresented minority groups. To validate the outreach activities, evaluation methods will be developed to determine the best practices associated with a K-6 outreach program. The goal of this project is to investigate the mechanistic details for the conversion of CO and dihydrogen to hydrocarbons by the FT process. Such mechanistic studies can both provide fundamental information on the FT process and point to new chemical pathways toward CO-derived C1 and C2 ligands. The project targets the C–C bond forming step in FT synthesis, which is not well understood, and centers on the deoxygenative and non-deoxygenative homocoupling of CO using a diiron siloxycarbyne compound. Specifically, CO bond scission and C–C bond formation steps will be evaluated. Starting with Fe2(COSiR3)(CO)L and related compounds the intermediates that form during C-O cleavage will be determined, their reactivity studied, and the mechanism of the subsequent generation of Fe2(CCO)L determined. In addition, the effect of functionalization of CO derived species will be evaluated. Once again using Fe2(COSiR3)(CO), the routes for functionalizing CO to generate C–X bonds will be targeted. In particular, the transfer the CCO fragment from Fe2(CCO)L to organic substrates, coupling of CO with the siloxycarbyne ligand in Fe2(COSiMe3)(CO)L, and the ability of diiron siloxycarbyne and diiron ketenylidene species to transfer the COSiMe3 and C2O ligands to exogenous substrates will be explored. 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.