Synthetic Studies of Sodium Aminodiboranate Salts with Electron- Withdrawing Substituents
SYNTHETIC STUDIES OF SODIUM AMINODIBORANATE SALTS WITH ELECTRON- WITHDRAWING SUBSTITUENTS BY CONNOR I. DALY THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry in the Graduate College of the University of Illinois at Urbana-Champaign, 2020 Urbana, Illinois Adviser: Professor Gregory S. Girolami ABSTRACT Magnesium diboride, MgB2, has the highest superconducting critical temperature of all traditional superconductors and is being considered for the fabrication of superconducting integrated circuits that can operate at higher temperatures than analogous niobium alloy circuits. A significant barrier to preparing superconducting MgB2 thin films, however, is that the films must be deposited below 300 °C to prevent Mg from subliming out of the film and causing loss of the superconducting properties. One approach to solve this problem is to prepare low- temperature chemical vapor deposition (CVD) precursors which would enable deposition of MgB2 at temperatures low enough to prevent loss of Mg from the thin film. In chapter 1, we describe the synthesis of three new sodium aminodiboranate salts, Na(BH3)2NRR′, with trimethylsilyl groups on nitrogen. These compounds – sodium N,N-bis- (trimethylsilyl)aminodiboranate, sodium N-trimethylsilylaminodiboranate, and sodium N- methyl-N-trimethylsilylaminodiboranate – were prepared by the reaction of μ-aminodiborane(6) species with sodium hydride. IR, 1H NMR, 13C NMR, and 11B NMR spectra are reported for all of these compounds, along with the crystal structures of N-trimethylsilylaminodiboranate and N- methyl-N-trimethylsilylaminodiboranate. Comparisons of 11B NMR chemical shifts suggest that steric, inductive, and hyperconjugative effects of the substituents on nitrogen are all in competition in these systems.
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