Two new potassium vanadium phosphates have been prepared and their structures have been determined from analysis of single crystal X-ray data. The two compounds, (\mathrm{K}{3}(\mathrm{VO})\left(\mathrm{V}{2} \mathrm{O}{3}\right)) (\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right)) and (\mathrm{K}{3}(\mathrm{VO})\left(\mathrm{HV}{2} \mathrm{O}{3}\right)\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right)), are isostructural, except for the incorporation of an extra hydrogen atom into the nearly identical frameworks. The structures consist of a threedimensional network of ([\mathrm{VO}]{n}) chains connected through phosphate groups to a (\left[\mathrm{V}{2} \mathrm{O}{3}\right]) moiety. Magnetic susceptibility experiments indicate that in the case of the di-hydrogen compound, there are no significant magnetic interactions between the three independent vanadium (IV) centers. Crystal data: for (\mathrm{K}{3}(\mathrm{VO})\left(\mathrm{V}{2} \mathrm{O}{3}\right)\left(\mathrm{PO}{4}\right){2}) (\left(\mathrm{HPO}{4}\right), M{\mathrm{r}}=620.02), orthorhombic space group Pnma (No. 62), (a=7.023(4) \AA, b=13.309(7) \AA, c=14.294(7) \AA, V=1336(2)) (\AA^{3}, Z=4, R=5.02 %), and (R_{\mathrm{w}}=5.24 %) for 1238 observed reflections ([I>3 \sigma(I)]); for (\mathrm{K}{3}(\mathrm{VO})\left(\mathrm{HV}{2} \mathrm{O}{3}\right)\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right), M_{\mathrm{r}}=) 621.04, orthorhombic space group Pnma (No. 62), (a=6.975(3)) (\AA, b=13.559(7) \AA, c=14.130(7) \AA, V=1336(1) \AA^{3}, Z=4), (R=6.02 %), and (R_{\mathrm{w}}=6.34 %) for 1465 observed reflections ([I\rangle) (3 \boldsymbol{\sigma}(I)] . \quad 1994) Academic Press, Inc.