Structure Determination for the Crystalline Phase of Triphenyl Phosphite by Means of Multi-Dimensional Solid-State NMR and X-Ray Diffraction

Jürgen Senker, Jens Lüdecke
2001 Zeitschrift für Naturforschung. B, A journal of chemical sciences  
The crystalline phase of triphenyl phosphite P(OC6H5)3 was investigated by means of 31P solid-state NMR and X-ray diffraction in a temperature range between 170 K and its melting point (Tm = 293 K). ID MAS NMR spectra exhibit one sharp central resonance indicating only one crystallographically unique molecule in the unit cell. A theoretical analysis concerning the shape of 2D exchange spectra for 1 = 1 /2 nuclei is presented. It is shown that if the exchange is caused by radio-frequency driven
more » ... pin-diffusion, this technique allows to discriminate rotational symmetry elements in crystalline solids. Used on crystalline triphenyl phosphite, 3-fold symmetry could be revealed clearly. Structure determination based on X-ray single crystal diffraction data collected at 191 K shows that triphenyl phosphite crystallises in hexagonal metric with space group R3̅(wR2= 8.3%, Z = 18) and one molecule in the asymmetric unit. This result is in excellent agreement with the NMR spectroscopic data. The lattice parameters at 200 K were determined to a = 37.887(1) and c = 5.7567(2) Å (V = 7156(1) Å3) by refining an X- ray powder-diffraction pattern. The structure of triphenylphosphite can be described as a close rod packing. The rods are formed by ecliptically arranged triphenylphosphite molecules. Due to the 3-fold rotoinversion axis the orientation of molecules in neighboured rods is antiparallel.
doi:10.1515/znb-2001-1101 fatcat:slidkuob6vd4ddpmzusjmuxb3i