John L. Miesel

NMR Studies of Restricted Rotation in Aminatophosphorus(1+) Salts

Abstract A series of aminatophosphorus(1+) salts were synthesized as potential fungicides. Proton NMR of a set of compounds 1 within this series were observed to show selective line broadening of the methylene protons indicating a dynamic process which is slow on the NMR time scale. X-ray crystal structures of two of the compounds in the series showed a relatively planar nitrogen eliminating nitrogen inversion as the source of the observed line broadening. The methylene protons appeared as a sharp doublet (3JPH = 3.6 Hz) at room temperature when R=OCH3, a broad singlet when R=OCF3, and a sharp multiplet consistent with the AB portion of an ABX (X = 31P) spin system when R=SCH. Examination of the temperature dependence of the spectra revealed that the observed lineshape and temperature effects were consistent with slow rotation about the N-Ph bond and dependent primarily upon the size of the substituent R. Thus the slow rotation was thought to be due to steric factors and not the influence of electronic ef...