α-Ba 2 P 2 O 7

Abstract

Key indicators: single-crystal X-ray study; T = 296 K; mean (P-O) = 0.001 A ˚ ; R factor = 0.021; wR factor = 0.046; data-to-parameter ratio = 69.4. Single crystals of-Ba 2 P 2 O 7 , dibarium diphosphate, were obtained by solid-state reaction. The orthorhombic structure is isotypic with-Sr 2 P 2 O 7 and is the second polymorph obtained for this composition. The structure is built from two different BaO 9 polyhedra (both with m symmetry), with Ba-O distances in the ranges 2.7585 (10)-3.0850 (6) and 2.5794 (13)-2.9313 (4) A ˚. These polyhedra are further linked by sharing corners along [010] and either edges or triangular faces perpendicularly to [010] to form the three-dimensional framework. This polyhedral linkage delimits large channels parallel to [010] where the P 2 O 7 diphosphate anions are located. These groups (symmetry m) are characterized by a P-O-P angle of 131.52 (9) and an eclipsed conformation. They are connected to the BaO 9 polyhedra through edges and corners. Related literature Besides crystals of the title compound, crystals of the hexagonal polymorph-Ba 2 P 2 O 7 were obtained (ElBelghitti et al. 1995). For isotypic structures, see: Hagman et al. (1968); Grenier & Masse (1977); Barbier & Echard (1998). For closely related structures, see: Elmarzouki et al. (1995). For poly-morphism in Ba 2 P 2 O 7 , see: McCauley & Hummel (1968); Mehdi et al. (1977); Bian et al. (2004); Kokhanovskii (2004). For a review of the crystal chemistry of diphosphates, see: Durif (1995). For applications of alkaline earth diphosphates, see: Pang et al. (2009); Peng et al. (2010). For an independent refinement of the-Ba 2 P 2 O 7 structure based on data from a hydrothermally grown crystal, see: Heyward et al. (2010). Experimental Crystal data Ba 2 P 2 O 7 M r = 448.62 Orthorhombic, Pnma a = 9.2875 (1) A ˚ b = 5.6139 (1) A ˚ c = 13.8064 (1) A ˚ V = 719.85 (2) A ˚ 3 Z = 4 Mo K radiation = 11.31 mm À1 T = 296 K 0.26 Â 0.14 Â 0.14 mm Data collection Bruker APEXII CCD diffractometer Absorption correction: multi-scan (SADABS; Bruker, 2008) T min = 0.155, T max = 0.205 18034 measured reflections 4304 independent reflections 3726 reflections with I > 2(I) R int = 0.028