Synthesis, purification, and characterization of phosphine oxides and their hydrogen peroxide adductsCCDC reference numbers 790886 and 845791 contain the crystallographic data for Bu3P&z.dbd;O (2) and Cy3P&z.dbd;O(H2O2) (4a), respectively. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c1dt11863c

• Main Authors: Hilliard, Casie R, Bhuvanesh, Nattamai, Gladysz, John A, Blmel, Janet
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c1dt11863c

Reactions of the tertiary phosphines R 3 P (R = Me, Bu, Oct, Cy, Ph) with 35% aqueous H 2 O 2 gives the corresponding oxides as the H 2 O 2 adducts R 3 P&z.dbd;O(H 2 O 2 ) x ( x = 0.51.0). Air oxidation leads to a mixture of products due to the insertion of oxygen into one or more PC bonds. 31 P NMR spectroscopy in solution and in the solid state, as well as IR spectroscopy reveal distinct features of the phosphine oxides as compared to their H 2 O 2 adducts. The single crystal X-ray analyses of Bu 3 P&z.dbd;O and [Cy 3 P&z.dbd;O(H 2 O 2 )] 2 show a P&z.dbd;O stacking motif for the phosphine oxide and a cyclic structure, in which the six oxygen atoms exhibit a chair conformation for the dimeric H 2 O 2 adduct. Different methods for the decomposition of the bound H 2 O 2 and the removal of the ensuing strongly adsorbed H 2 O are evaluated. Treating R 3 P&z.dbd;O(H 2 O 2 ) x with molecular sieves destroys the bound H 2 O 2 safely under mild conditions (room temperature, toluene) within one hour and quantitatively removes the adsorbed H 2 O from the hygroscopic phosphine oxides within four hours. At 60 C the entire decomposition/drying process is complete within one hour. The selective oxidation of tertiary phosphines and efficient one-step removal of adsorbed H 2 O 2 and H 2 O is explored, and it is demonstrated by liquid- and solid-state NMR, IR, and single crystal X-ray diffraction that phosphine oxides and their H 2 O 2 adducts are distinctly different species.