N,N′-Diphenylthiourea acetone monosolvate

In the title compound, C13H12N2S·C3H6O, the phenyl rings of the thiourea molecule are in syn and anti positions in relation to the C=S bond. Two molecules are connected by N—H⋯S=C hydrogen bonds into a centrosymmetric dimer. An additional N—H⋯O=C hydrogen bond to the acetone solvent molecule and some weak C—H⋯π interactions reinforce the crystal structure.

When N,N'-diphenylthiourea cocrystalizes with acetone in Pbca space group the centrosymmetric dimer is also formed as it is common among compounds containing S═CR 1 -NR 2 -H group. There is at least 109 such structures deposited in CSD. This motif is particularly common among N-acyl-N'-arylureas and thioureas (Okuniewski et al., 2010). When monosubstituted N-phenylthiourea is considered, chains of molecules can be found (Shen & Xu, 2004). In the title compound an additional N-H···O═C hydrogen bond to acetone is formed stabilizing the structure. Crystals are well formed and grow up to several milimeters in just one day.
There is no π···π stacking in this structure, but some weak C-H···π interactions can be found (see Tab. 1). Melting point, 154°C, is the same as that for pure N,N'-diphenylthiourea. This is because crystals very quickly loose acetone molecules before melting (even at room temperature) and became colourless powder of pure thiourea derivative.
Experimental 1.82 g (8 mmol) of commercially available N,N'-diphenylthiourea was added to 25 ml of acetone and gently heated while stirring. After 5 min nearly full dissolution was observed. The mixture was allowed to cool and then was filtered. The filtrate was left for crystalization at room temperature. After one day well formed, colourless shiny crystals were collected. Yield -1.86 g (81%).

Refinement
Hydrogen atoms were placed at calculated positions (d CH = 0.95-0.98 Å) and were treated as riding on their parent atoms, with U(H) set to 1.2-1.5 times U eq (C). The N-H distances were restrained to 0.88 (1) Å. Fig. 1

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The  (4). Distance calculations were done using PLATON (Spek, 2009 as those based on F, and R-factors based on ALL data will be even larger.