Bis(bipyridyl)silicon(IV) Diols as Potential Dual Hydrogen Bond Donors for Catalysis
1 online resource (90 pages) : PDF
University of North Carolina at Charlotte
Hydrogen bond donors (HBDs) have been explored as potential catalysts for the 1,4-conjugate addition and Diels-Alder reactions. HBD catalysis, which relies on Brønsted acid catalytic sites, is being explored as an oxygen and moisture stable alternative to transition metal catalysis. While most of the HBD catalysis field is based on organic catalysts, a few groups have explored silicon diols as potential dual hydrogen bond (DHB) catalysts.In this project, two analogs of [Si(bpy)2(OH)2]2+ were synthesized using different substituted 2,2’-bipyridine ligands including: 4,4’-dimethyl-2,2’-bipyridine (Me2bpy) and 4,4’-bis(tert-butyl)-2,2’-bipyridine (tBu2bpy). Multinuclear Nuclear Magnetic Resonance (NMR), Infrared (IR) spectroscopies, and Elemental Analysis (EA) were used to characterize the complexes. X-ray crystallography was used to study the two compounds in the solid state. NMR kinetic studies were completed to determine if the silicon diols exhibited catalytic ability. A 1,4-conjugate addition reaction of N-methylindole (NMI) to trans-β-nitrostyrene (BNS) was used as the test reaction. The data suggest that the hexacoordinate silicon diols act as HBDs and have catalytic activity. [Si(tBu2bpy)2(OH)2](PF6)2 was found to have superior catalytic properties over other silicon diols. Solvent and ions in solution effect the catalytic ability. Enantiomeric enrichment of [Si(Me2bpy)2(OH)2]I2 was successful and chiral catalysis is a future direction for the synthesized silicon diols.
CATALYSISHYDROGEN BOND DONORSSILICON DIOLS
Donovan-Merkert, BernadetteRabinovich, DanielNesmelova, Irina
Thesis (M.S.)--University of North Carolina at Charlotte, 2016.
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