trans-Tetraaquabis{(E)-2-cyano-1-[(ethoxycarbonyl)methylsulfanyl]-2-(1-naphthylaminocarbonyl)ethene-1-thiolato}calcium(II) diethyl ether disolvate

In the title compound, [Ca(C18H15N2O3S2)(H2O)4]·2C4H10O, the Ca atom, which lies on an inversion centre, is coordinated octahedrally by four water molecules and two anions of the ketene dithioacetal, the donor atoms of which are the amidic carbonyl O atoms. The central backbone of the ligands (excluding the naphthalene and oxoethyl groups) is essentially planar (r.m.s. deviation 0.035 Å). Intramolecular hydrogen bonds are observed from the NH group to the formally ‘thiolate’ S atom and from one coordinated water to the nitrile group and to the ether O atom. Intermolecular hydrogen bonds from the second independent water molecule to the thiolate S atom and the side-chain oxo group connect the molecules in chains parallel to the a axis.

In the title compound, [Ca(C 18 H 15 N 2 O 3 S 2 )(H 2 O) 4 ]Á2C 4 H 10 O, the Ca atom, which lies on an inversion centre, is coordinated octahedrally by four water molecules and two anions of the ketene dithioacetal, the donor atoms of which are the amidic carbonyl O atoms. The central backbone of the ligands (excluding the naphthalene and oxoethyl groups) is essentially planar (r.m.s. deviation 0.035 Å ). Intramolecular hydrogen bonds are observed from the NH group to the formally 'thiolate' S atom and from one coordinated water to the nitrile group and to the ether O atom. Intermolecular hydrogen bonds from the second independent water molecule to the thiolate S atom and the side-chain oxo group connect the molecules in chains parallel to the a axis.

Related literature
For our studies exploring the synthetic potential of ketene dithioacetals for synthesizing new classes of novel antimetabolic agents, see: Elgemeie & Sood (2006); Elgemeie et al. (2008Elgemeie et al. ( , 2009. For our reports of successful approaches for the synthesis of mercaptopurine and pyrimidine analogues by the reaction of ketene dithioacetals with active methylene functions, see: Elgemeie (2003); Elgemeie et al. (2004Elgemeie et al. ( , 2007.

Experimental
Crystal data [Ca(C 18 (Elgemeie, 2003;Elgemeie et al., 2004Elgemeie et al., , 2007. In conjunction of this work, we report here a novel calcium salt (I) of a ketene dithioacetal. The structure of (I) was established on the basis of its elemental analysis and spectral data (see Experimental). In order to establish unambiguously the structure of the product, the crystal structure was determined. The X-ray analysis confirms the exclusive presence of the form (I) in the solid state ( Figure 1).
The structure consists of a calcium ion on an inversion centre, coordinated octahedrally by four water molecules and two anions of the ketene dithioacetal; the latter coordinate via the amidic carbonyl oxygen O1, with Ca-O1 2.2696 (9) Å. The asymmetric unit also contains one molecule of diethyl ether.
Intramolecular hydrogen bonds (Table 2) are observed from the NH function to the formally thiolate sulfur and from a hydrogen of the coordinated water O1W to the nitrile N. Additionally, the ether molecules are connected by a hydrogen bond from the same water to the ether oxygen. Intramolecular H bonds from the second water to the thiolate sulfur and the 2-oxo function connect the molecules to form chains parallel to the a axis ( Fig. 2).

Refinement
Crystal data [Ca(C 18   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.