Hydrothermal synthesis and X-ray powder structure determination of a novel layered tin(IV) phosphate, Sn(HPO4)2·(NH3)0.4(H2O)0.6

A novel layered tin(IV) phosphate, Sn(HPO4)2·(NH3)0.4(H2O)0.6, was synthesized under mild hydrothermal conditions. The unit cell is trigonal, a=4.9751(2) Å, c=22.5983(8) Å, space group R3̄, Z=3. The interlayer water and ammonia molecules are disordered and were both located on the same crystallographic site. This compound is the first example within the well-known family of α-metal(IV) phosphates of a non monoclinic phase stable at room temperature. The polymorphism of these compounds would explain several of the bibliographical discrepancies detected in the description of its physical–chemical properties.