The crystal structure of SnP3 and a note on the crystal structure of GeP3

SnP3 crystallizes in the trigonal space group R3m with six formula units in a unit cell of dimensions a = 7.378Å and c = 10.512Å. The detailed atomic arrangement has been determined from three-dimensional single crystal X ray data. The structure is characterized as a layer structure related to the As-type structure (A7). The identical layers consist of puckered P6 rings connected by Sn atoms. The centers of the P6 rings are situated between Sn atoms of adjacent layers. This leads to a distorted octahedral coordination for the tin atoms with three phosphorus atoms belonging to the same layer as the tin atom at a distance of 2.662 Å, and three phosphorus atoms in an adjacent layer at a distance of 2.925 Å. The PP bond length within the rings is 2.222 Å and the PPP bond angle is 99.1°.