ANION EFFECTS IN HOMOGENOUS PALLADIUM CATALYSIS AND LUMINESCENT PROPERTIES OF COPPER(I) COMPLEXES BEARING A WEAKLY-COORDINATING ANIONIC N-HETEROCYCLIC CARBENE LIGAND

Abstract

The general theme of this dissertation concerns how the locality of an anionic moiety, be it a weakly coordinating anion or an anionic ligand, affect the spectroscopic and structural properties of organotransition metal complexes. Probing the columbic interactions between traditional and novel weakly coordinating anions with transition metal complexes, enables synthetic chemists to select anions that can improve catalytic transformations, impart stability of reactive intermediates, or develop new mechanistic insights. Additionally, presented herein is the manifestation of a new class of luminescent copper complexes which bear a weakly coordinating anionic N-heterocyclic carbene ligand.Firstly, a qualitative scale of coordinating ability is prepared by pairing traditional anions and weakly-coordinating anions with [Pd(IPr)(C(O)C9H6N)]+. NMR, IR, Computation, %Vbur, and X-ray crystallographic techniques are used to study the solution and solid-state interactions of these salts. During this study, a novel anion, denoted IMP- is prepared where two B(C6F5) groups are bridged by a phenyl imidazole core. Ultimately, it was found that sterics dictate coordinating ability observed by NMR and %Vbur, while IR and computation show the electronic effects of anion coordination. Continuing our understanding of the interplay between cation and anion, anionic Au(I) complexes are synthesized and paired with the same palladium cation in our first investigation. The framework of these Au(I) anions features a weakly coordinating N-heterocyclic carbene ligand that bears a borate moiety of the NHC backbone. Facile dissociation of a dimethyl sulfide ligand with metal alkoxide/phenoxides/thiophenoxides affords sodium or potassium salts. With these anions in hand, ion pairs are isolated in polar solvents and in the solid state. Au anions reside in the outer sphere of the palladium cation; like that of weakly coordinating anions such as BArF4-. Lastly, Luminescent group 11 organometallic complexes featuring N-heterocyclic carbene (NHC) ligands offer a swath of applications; catalytic transformations in organic chemistry to inorganic material uses in light emitting technologies. Conventional complexes are of the type NHC-M-X, where M is Cu, Ag, or Au and X represents anionic ligands that are often prone to hydrolysis. In this dissertation, Cu(I) complexes featuring this N- heterocyclic carbene ligand bearing a weakly coordinating anionic substituent (WCA-NHC) are prepared. (WCA-NHC)-M-L are air and moisture stable and differ from conventional NHC-M-X in that the metal can be supported by 2 datively-bound ligands. Initial computation reveals a change in dipole of (WCA-NHC)-Cu-PR3 charge transfer compared to that of reported NHC-M-X. By exchanging triphenylphosphine for diphenyl-2-pyridyl phosphine, we can change the emission wavelength by about 200 nm.