High-resolution solid-state 29Si and 31P NMR of silicon-phosphorous compounds containing six-coordinated silicon

Abstract

29Si and 31P chemical-shift data for Si(HPO 4) 2·H 2O and SiP 2O 2 were obtained from magic angle spinning (MAS) NMR spectra. According to the 29Si chemical shifts, the silicon atoms are six-coordinated in both compounds. There are two non-equivalent silicon-oxygen octahedra in the structure of SiP 2O 2, but there is only one in Si(HPO 4) 2·H 2O. From 31P MAS NMR spectra it is possible to distinguish four different PO 4 tetrahedra in SiP 2O 7 and two in Si(HPO 4) 2·H 2O. Additional information on the symmetry of the PO 4 tetrahedra is obtained from broad line 31P NMR spectra.