The crystal structures of (Z)-(ethene-1,2-diyl)bis(diphenylphosphine sulfide), C26H22P2S2 (I), along with its complex with PtII dichloride, dichlorido[(Z)-(ethene-1,2-diyl)bis(diphenylphosphine sulfide)-κ2 S,S′]platinum(II), [PtCl2(C26H22P2S2)] (II), are described here. Compound I features P=S bond lengths of 1.9571 (15) and 1.9529 (15) Å, with a torsion angle of 166.24 (7)° between the two phosphine sulfide groups. The crystal of compound I features both intramolecular C—H...S hydrogen bonds and π–π interactions. Molecules of compound I are held together with intermolecular π–π and C—H...π interactions to form chains that run parallel to the z-axis. The intermolecular C—H...π interaction has a H...Cg distance of 2.63 Å, a D...Cg distance of 3.573 (5) Å and a D—H...Cg angle of 171° (where Cg refers to the centroid of one of the phenyl rings). These chains are linked by relatively long C—H...S hydrogen bonds with D...A distances of 3.367 (4) and 3.394 (4) Å with D—H...A angles of 113 and 115°. Compound II features Pt—Cl and Pt—S bond lengths of 2.3226 (19) and 2.2712 (19) Å, with a P=S bond length of 2.012 (3) Å. The PtII center adopts a square-planar geometry, with Cl—Pt—Cl and S—Pt—S bond angles of 90.34 (10) and 97.19 (10)°, respectively. Molecules of compound II are linked in the crystal by intermolecular C—H...Cl and C—H...S hydrogen bonds.

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis(diphenylphosphanyl)ethylene, namely, 1,2-(ethene-1,2-diyl)bis(diphenylphoshpine sulfide/selenide), C26H22P2S1.13Se0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between F obs 2 and F calc 2, plots of |F obs| vs |F calc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of interatomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.