Received 8 May 2013
A new iron phosphate, rubidium copper(II) iron(III) bis(phosphate), RbCuFe(PO4)2, has been synthesized as single crystals by the flux method. This compound is isostructural with KCuFe(PO4)2 [Badri et al. (2011), J. Solid State Chem. 184, 937-944]. Its structure is built up from Cu2O8 units of edge-sharing CuO5 polyhedra, interconnected by FeO6 octahedra through common corners to form undulating chains that extend infinitely along the  and [01-1] directions. The linkage of such chains is ensured by the PO4 tetraedra and the resulting three-dimensional framework forms quasi-elliptic tunnels parallel to the  direction in which the Rb+ cations are located.
For the physical properties of iron phosphates, see: Elbouaanani et al. (2002). For the structural chemistry of iron phosphates, see: Moore (1970); Gleitzer (1991). For rubidium iron phosphates, see: Hidouri et al. (2010). The title compound is isostructural with KCuFe(PO4)2 (Badri et al., 2011) and K(Fe,Mg)(PO4)2 (Yatskin et al., 2012). For P-O distances in monophosphate groups, see: Baur (1974). For ionic radii, see: Shannon (1976).
Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2226 ).
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