Abstracts Category : Other

The Use of Monocarba-closo-dodecaborate Carborane Anion in Catalyst Design

by Allen Chan

Abstract of the DissertationThe Use of Monocarba-closo-dodecaborate Carborane Anion in Catalyst DesignbyAllen L. ChanDoctor of Philosophy, Graduate Program in ChemistryUniversity of California, Riverside, December 2016Dr. Vincent Lavallo, ChairpersonCarboranes are polyhedral boron-carbon molecular clusters stabilized by electron-delocalized covalent bonding throughout the skeletal framework. Once thought of as novel curiosities due to their structure and bonding, carboranes have now been applied in many diverse fields, from medicine to nanoscale engineering. Of particular interest is the icosahedral monocarba-closo-dodecaborate(-) (HCB11H11 anion) carborane and its derivatives due to their many unique properties. This type of carborane is well known for its extremely low nucleophilicity and considered the most weakly coordinating of all known anions. Also, these carboranes are extremely difficult to oxidize and most are stable to the most aggressive reagents. Because of these unique properties, we explore the use of functionalized carboranes as ligand R-groups in transition metal complexes for their eventual application in catalysis. Organic azides are invaluable building blocks for synthetic chemists. Herein we report the synthesis of various carboranyl azides and some unusual reactivity during the carboranyl azide synthesis. The synthesis and characterization of the parent carboranyl azide (Li+N3CB11H11-) hexabrominated carboranyl azide (Li+N3CB11Br6-), the perbrominated carboranyl azide (Li+N3CB11Br11-), and the perchlorinated carboranyl azide (Li+N3CB11Cl11-) are reported. We also report unique reactivity involving these new compounds, such as room temperature B-Cl activation of the perchlorinated carba-closo-dodecaborate anion.Though the formation of Schiff bases from amines have long been used in organic chemistry, the condensation of amines to form imines with the carboranyl amine had not yet been reported at the time. Here, we report examples of imine formation with carboranyl amine as well as metal complex formation with carboranyl imines. Also, we report the synthesis of an N-hetereocyclic carbene with the hexabrominated carborane. Phosphine ligands have been used extensively as ligands in metal catalyzed cross-coupling reactions. Metal catalyzed cross-coupling reactions are a mainstay of synthetic chemistry. Here, we report the synthesis of various carboranyl phosphine ligands and their use as R-ligands in Pd catalyzed coupling reactions. We also disclose on new and previously unreported activity with carboranyl Pd complexes with different substrates.