Iminophosphorane-substituted proton sponges. Part 5. Structures in the solid state. Correlation between solid state31P MAS NMR spectra and crystal structures

Abstract

The 31P NMR spectra of protonated Iminophosphorane-substituted proton sponges of known crystal structure have been recorded in the solid state under the conditions of magic angle spinning (MAS) and 1H-decoupling. Variable temperature experiments and a comparison with the averaged 31P chemical shifts in solution show that no proton transfer occurs in the crystal, even when strong intramolecular hydrogen bonds are present. Good agreement between the NMR results and the X-ray structures gives weight to structural predictions based on solid state 31P MAS NMR spectroscopy, for compounds which do not yield suitable monocrystals.