Mahsa Eghbali Toularoud - Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
Mehrdad Pourayoubi - Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
Michal Dušek - Institute of Physics of the Czech Academy of Sciences, Na Slovance ۲, ۱۸۲ ۲۱ Prague ۸, Czech Republic
Václav Eigner - Institute of Physics of the Czech Academy of Sciences, Na Slovance ۲, ۱۸۲ ۲۱ Prague ۸, Czech Republic

The cyclic compound [S-(–)-(C6H5)CH(CH3)NP(S)NH(S)-(–)-CH(CH3)(C6H5)]2,H2O, or C32H38N4P2S2,H2O is a member of a class of molecules that may be used for extraction of metals. The literature shows many studies of the bidentate phosphorus ligands HN [P (E) R2]2 (E: O, S) [1] and RN [P (E) R2]2 [2]. The title compound was characterized in the solid state by IR and X-ray crystallography and in the solution with calculation of the specific optical rotation. The compound crystallizes in the chiral space group P212121 and the asymmetric unit of the structure consists of four symmetry-independent cyclodiphosphazanes and four water (H2O) molecules.In the molecular structure, each phosphorus atom is bonded to one sulfur and three nitrogen atoms. The P–N bond distances in the ring are longer than the P–NH distances, and the P–S distances are in the range of 1.9376 (9) to 1.9434 (9) Å. These geometric parameters are in agreement with those observed in related compounds [3]. In the crystal structure, molecules are linked through N–H…OW hydrogen bonds in a tape arrangement along the c axis (OW is the oxygen of H2O molecule). This pattern includes an ?21(8) graph-set motif, formed through (NH…)(NH…)OW grouping. The prevalence of these interactions is illustrated by an analysis of the three-dimensional Hirshfeld surface (HS) and by two-dimensional fingerprint plots (FP) for one of the cyclodiphosphazane molecules in the asymmetric unit. The relative contributions of different interactions in the HS are: H…H 69.0%, C…H/H…C 17.4% and S…H/H…S 10.6%.