A Foundational Study of a New Synthetic Method of Metal Carbonyl Clusters

Abstract

Traditional" Metal Carbonyl Clusters (MCCs) contain a framework of multiple metal atoms bound together through formal metal-metal (M-M) bonds. Current methods of synthesis result in different cluster sizes and lack a method to control growth. This project proposes a new method of MCC synthesis to build larger structures utilizing secondary non-covalent interactions to develop "non-traditional" MCCs. The N,N'-diarylurea moiety is a strong hydrogen bond donor/acceptor that can induce self-assembly into larger secondary structures. The union of metal carbonyl and urea chemistry provides a potential method of "non-traditional" MCC synthesis. This proof of concept experiment will elucidate foundational information such as: reduction-oxidation potentials, chemical organization, chemical structure, and binding constants. The x-ray crystal structures detail a nearly planar molecular organization and refute the formation of urea ribbons due to a stabilizing intramolecular hydrogen bond interaction. Stabilizing π-π stacking and a ureaπ stacking interactions were observed as a result of the planar orientation. A titration study confirms the strong anion binding capability of the metal carbonyl appended urea moiety and confirms anion binding as a possible method of coordinating multiple units together to build "non-traditional" MCCs. The π-π interactions and urea-π interactions were observed as the largest contributor to the molecular structure and as a result, the appended group 6 metal centers are separated by distances between 6.00 Å and 8.00 Å. The close contact between metal nuclei has the potential to allow for electrochemical communication albeit not with these compounds. The characterization and synthesis of 1,3-bis(pvii isocyanophenyl)urea and its group 6 metal containing derivatives provided sufficient data to lay a solid foundation for continuing research.