The Absence of Proton Transfer in the 2 : 1 Crystalline Adduct of Triphenylphosphine Oxide with Sulfuric Acid

摘要

The 2 : 1 crystalline adduct of triphenylphosphine oxide with sulfuric acid Pl_3O centre dot 0.5 H_2SO_4 (I) was studied by X-ray diffraction. The structure of I (space group Fdd2, a = 20.112 A, b = 32.670 A, c = 10.042 A, Z= 16) was refined by full-matrix least-squares calculations in the anisotropic approximation to R = 0.056 for all 3116 independent reflections (CAD4 automated diffractometer, lambda MoK_alpha). Unlike two previous X-ray diffraction analyses of this crystalline adduct, this study showed that compound I is neutral; i.e., no proton transfer from H_2SO_4 to Ph_3PO is involved. The H_2SO_4 molecule in structure I is statistically disordered relative to crystallographic axis 2, the occupancy of each atom position being 0.5. The H_2SO_4 molecule forms two disordered S-O-H…O=P hydrogen bonds (one strong and one somewhat weaker) with two symmetric Ph_3PO molecules.