Bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2(bihyat)) was synthesized then coordinated to a molybdenum center to form MoO2(bihyat) (C9H14MoN6O5, 38% yield, a = 18.7, b = 10.0, c = 15.2, a = 90, b = 107.5, g = 90.0, r = 6.22%). The MoO2(bihyat) compound was used to oxidize thioanisole and various phosphines. MoO2(bihyat) oxidizes thioanisole with excess hydrogen peroxide to the corresponding sulfoxide and sulfone. The oxidation of phosphines causes the catalyst to fall apart but is still able, in certain cases, to convert five equivalents to the respective phosphine oxide. It was determined via tagged H218O and 31P-NMR that the oxygen on the phosphine does not come from the H2O. The O2 (g) percent was modulated (0%, 20%, 50%, and 100%) and it was determined that the oxygen source was neither the ambient or added dioxygen. The ligand itself seems to be the only plausible source for the oxygen atom transfer reaction. This causes the ligand to fall off and the free ligands' terminal amides to be converted to amines. The reduced free triazine amine ligand has not yet ben proven to exist by authentic addition. However, simulated DFT (B3LYP/6-311G LANL2DZ) NMR spectra and 1H-13C/1H-1H 2D-NMR show promising results for this chemical to exist in solution. When the phosphine substrate decreased in size, from triphenyl to methyldiphenyl, the reaction rate increased dramatically. The reaction with methyldiphenylphosphine seems to follow a different mechanism due to it fitting to a pseudo first-order exponential.

Mechanistic investigation of the molybdenum catalyzed oxidation of key phosphines and sulfides

251st National Meeting (2016)

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