Studies of silicophosphate derivatives by 31P-->29Si CP MAS NMR

We show that it is possible to efficiently transfer magnetization from ³¹P to ²⁹Si, using variable amplitude CP MAS experiment. This experiment is demonstrated by using Si₅O(PO₄)₆, the synthesis protocol of which is described. From the obtained results, we show that the experiment allows the spectral edition of ²⁹Si spectra from ³¹P→²⁹Si CP, enabling the studies of derivatives involving Si–O–P linkages, such as phosphosilicate glasses, microporous silicoaluminophosphates (SAPO) and bioactive phosphosilicates.     

Silicophosphates of Rhodium and Indium

Single crystals of Rh(Si₂O)(PO₄)₃ and In₄(Si₂O) · (PO₄)₆ were prepared by chemical transport reactions in silica tubes and their structures were determined. Crystal data of Rh(Si₂O)(PO₄)₃: trigonal, space group P 3 c1, a = 8.088(3) Å, c = 8.740(2) Å, Z = 2, R(F²) = 0.0379, R_w(F²) = 0.0518 for 601 unique reflections. In₄(Si₂O)(PO₄)₆: hexagonal, space group P6₃/m, a = 8.5149(10) Å, c = 7.7481(12) Å, Z = 1, R(F²) = 0.0436, R_w(F²) = 0.0522 for 509 unique reflections. Both of the compounds have hexagonal close packed array of phosphate groups with metal atoms and SiOSi units in the octahedral interstices, where the SiOSi units show occupational disorder. The structure of the indium compound is considered to be a disordered structure of the reported Mo₄Si₂P₆O₁₃ structure, and contains confacial bioctahedral units.