Organometallic chemistry is highly dependent upon the ligands which are employed on a metal's surface. These ligands control steric bulk and electronics of the metal center which can change the reactivity of the organometallic complex. Ligands that are standard in organometallic chemistry include phosphine ligands. These phosphine ligands have been utilized in the field since the 1960's and have shaped the development of many key organometallic catalysts. Phosphine ligands are easily functionalized and highly reactive. This increased reactivity, however, causes severe limitations as phosphine ligands are often unstable under standard benchtop conditions and must be handled both air and moisture free environments. To combat some of these issues new ligand types have emerged such as N-heterocyclic carbene ligands. These ligands are found to possess similar reactivity in terms of electron and steric influences but can be prepared and used on the benchtop. In this work we highlight a dual N-heterocyclic carbene/phosphine ligand which is obtained from an accessible 2-phosphinoimidazole. These 2-phsophinoimidazole ligands can undergo a transformation in the presence of a proton source. The proton source will cause the disassociation of the C-P bond forming a NHC-phosphine complex. Addition of a metal source to the NHC-phosphonium complex causes a NHC/phosphine metal complex, which upon further investigation was found to be catalytically active. This activity was tested in various cross coupling reactions which include Suzuki, Heck, and Sonogashira. Highlights of these results include the extreme functionalization of these 2-phosphinioimidazole ligands which can produce new aryl groups on the NHC, a free N-H bond on the imidazole which can be deprotonated or influence intermolecular forces with substrates, replacing the moieties on the phosphine, and finally the ability to transform in situ with the addition of a common alcohol. Each of these functionalization's are explained below along with their reactivity to isolate a wide variety of substrates. In addition to the work above a collaboration with Rio Tinto and the Madsen Lab at BYU is discussed. This work involves the concerns of land managers and their ability to restore landscapes that have been destroyed through a variety of issues including fire, mining, and invasive species. These ecological pressures cause land managers to search for native plants to seed on a landscape. Issues arise when using natives, however, because of their inability to quickly germinate and establish on a landscape. This is caused by dormancy issues where an antagonistic relationship between gibberellic acid and abscisic acid where the overproduction of one over the other results in dormant native plants. We have invented a methodology to use slow releasing polymers to hijack this system and deliver gibberellic acid to a seed causing it to germinate regardless of external stimuli. Our results show significant improvement in native Penstemon species with no side effects to the plant growth and establishment.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-11292 |
| Date | 20 March 2024 |
| Creators | Larson, Alexandra Jean Setelin |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | https://lib.byu.edu/about/copyright/ |
Page generated in 0.0027 seconds