2016. 57, 4 – UDC 548.73:541.49:546.72 CRYSTAL STRUCTURE OF NOVEL LAYERED IRON ARSENATE-OXALATE (NH4)3K3[Fe2(HAsO4)2(C2O4)4] 2H2O N. Ouerfelli1, 2, H. Chebbi1, 3, M. Faouzi Zid 1 1Universitй de Tunis El Manar, Facultй des Sciences de Tunis, Laboratoire de Matйriaux et Cristallochimie, Tunis, Tunisia 2Universitй de Tunis Carthage, Institut Prйparatoire aux Etudes dIngйnieur de Bizerte, Bizerte, Tunisia 3Universitй de Monastir, Institut Prйparatoire aux Etudes dIngйnieurs de Monastir, Monastir, Tunisia E-mail: chebhamouda@yahoo.fr Received March 3, 2015 A new open-framework structure of iron arsenate-oxalate (NH4)3K3[Fe2(HAsO4)2(C2O4)4] 2H2O (I) is synthesized by slow evaporation and structurally characterized by single crystal X-ray diffraction methods. <...> Its crystal structure consists of two crystallographically independent bishydrogenarsenato tetraoxalato diiron(III) anions, both located on centres of inversion, while the potassium and ammonium cations and water molecules are located in general positions. <...> These moieties are connected through N—H…O and O—H…O hydrogen bonds to form infinity of layers parallel to the (101) plane, thus leading to a two-dimensional open framework. <...> In chemistry, the importance to synthesize new open-framework materials has attracted increasing attention. <...> The incorporation of oxalate anions into the iron-phosphate frameworks expands the structural complexity and properties through their coordinating propensities and geometries. <...> According to the literature, many researches on metal—oxalate hybrid compounds are carried out due to their original structures and potential applications as co-precipitation precursors [ 1, 2 ], in heterogeneous catalysis [ 3, 4 ] (in sorption and ionic exchange processes), in conductivity and magnetism [ 5—7], and as Li-ion batteries [ 8—10]. <...> The oxalate anion is a key bridging element in several molecular magnetic materials. <...> Here we report the synthesis and crystal structure of the first iron arsenate-oxalate with the inorganic cation: (NH4)3K3[Fe2(HAsO4)2(C2O4)4]2H2O (I). <...> Crystals of I were obtained by slow evaporation. <...> The compound was synthesized from a mixture <...>