(\mathrm{RbVP}{2} \mathrm{~S}{7}) has been obtained as black platelets by heating the elements in stoichiometric proportions at (550^{\circ} \mathrm{C}) under vacuum in evacuated silica tubes for 21 days. It crystallizes in the monoclinic symmetry, space group (C 2), with the parameters (a=858.30(9) \mathrm{pm}, b=956.8(1) \mathrm{pm}, c=646.94(3) \mathrm{pm}), and (\beta=) (98.22(1)^{\circ}, V=525.8(1) \times 10^{6} \mathrm{pm}^{3}). The refinements led to a reliability factor of (2.7 %) for 933 independent reffections and 56 variables. The structure of (\mathrm{RbVP}{2} \mathrm{~S}{7}) is built from (\mathrm{VS}{6}) octahedra and (\mathrm{PS}{4}) tetrahedra. The tetrahedra, which form (\mathrm{P}{2} \mathrm{~S}{7}) groups through apex sharing, bind the (\mathrm{VS}{6}) octahedra through mutual apexes or edges. The rubidium atom occupies the center of a sulfur bicapped trigonal prism, thus exhibiting a coordination of eight. Within its site, the rubidium important displacement can only be described by using a third-order anharmonic tensor (Prometheus program). The atomic distances and magnetic properties are in agreement with the (\mathrm{Rb}^{l} \mathrm{~V}^{\mathrm{III}}\left(\mathrm{P}{2} \mathrm{~S}_{7}\right)^{-\mathrm{IV}}) charge balance. 1993 Academic Press, Inc.