X-ray, 31P CP/MAS, and single-crystal NMR studies, and 31P DFT GIAO calculations of inclusion complexes of bis[6-O,6-O-(1,2:3,4- diisopropylidene-α-D-galactopyranosyl)thiophosphoryl] disulfide: the importance of C-H...S=P contacts in the solid state

Bis[6-O,6-O-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl) thiophosphoryl] disulfide shows a strong tendency to form inclusion compounds. The crystal and molecular structure of eight different solvates was established by X-ray analysis. The results indicate three different types of disulfide arrangements in the crystal lattice. By means of 31P CP/MAS NMR experiments the principal values δ 11, δ 22, and δ 33 of the 31P chemical shift tensor were obtained for each form. The orientation of its principal axes with respect to a molecular frame was investigated by means of 31P CP and single-crystal NMR for the complex with propan-2-ol. The principal axis 1 of both chemically equivalent phosphorus atoms is nearly parallel to the P-S bond and the principal axis 3 is very close to the P=S bond. DFT GIAO calculations of the model compound (EtO)2(S)P1SSP2(S)-(OEt)2 allowed assignment of the experimental chemical shift curves to the magnetically nonequivalent atoms P1 and P2. The maximum difference between calculated angles [symbol: see text] i-P-X)calcd and experimental angles [symbol: see text] i-P-X)exptl is 8.3 degrees and the rms distance 3.8 degrees (i = principal axes 1, 2, 3; X = S, -S-, -O1-, -O2-). The influence of C-H...S weak hydrogen bonding on phosphorus shielding was tested theoretically (31P DFT GIAO) employing the dimethoxythiophosphoryl disulfide.CH4 complex as a model compound. The sensitivity of 31P delta ii parameters to intermolecular forces is demonstrated