N′-Benzoyl-N,N-diethylthiourea: a monoclinic polymorph

In the crystal of the title compound, C12H16N2OS, inversion dimers linked by pairs of N—H⋯S hydrogen bonds occur, generating R 2 2(8) loops. The molecules are also linked by weak C—H⋯O hydrogen bonds. The structure is isostructural with that of N′-benzoyl-N,N-diethylselenourea [Bruce et al. (2007 ▶). New J. Chem. 31, 1647–1653].

The structure of another polymorph of (1) is deposited as a private communication in the CCDC database, Bolte & Fink (2003). This is reported as crystallising in spacegroup P1 with four molecules in the asymmetric unit. In this compound the molecules are linked into two sets of C4 chains by N-H···O hydrogen bonds. These chains are formed by hydrogen bonded pairs of molecules in which the the N1-C2-N3-C4 torsion angles (our) numbering) are 78.6 (4)° and -80.8 (3)°i n one pair and 78.7 (4)° and -81.9 (3)°. In these conformations the O atom is in a favourable position for forming N-H···O hydrogen bonds. In (1) the N1-C2-N3-C4 torsion angle is -71.43 (14)° and the S atom then becomes more accessible as an acceptor for a hydrogen bond and the O atom less so. Related thiourea structures are discussed in Braun et al., (1987).

Experimental
The title compound was prepared as described by Hartmann & Reuther (1973) and Beyer et al. (1975). The reaction as described in these papers produced yellow plates of (I), which after washing in ethanol at room temperature, were suitable for X-ray diffraction without recrystallisation.

Refinement
H atoms were treated as riding atoms with C-H(aromatic), 0.95 Å, C-H(CH 2 ), 0.99 Å. The atom attached to N1 was located on a difference map at a distance of 0.9138Å and was fixed as a riding atom at this distance.  A view of the R 2 2 (8) dimer lying across the centre-of symmetry at (0.5,0.5,0.5). Atoms marked with an asterisk,*, are in the molecule at (1-x,1-y,1-z). Hydrogen atoms not involved in the hydrogen bonding are omitted for the sake of clarity.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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.