O,O-Dimethyl O-(4-sulfamoylphenyl) phosphorothioate (cythioate)

The title molecule, C8H12NO5PS2, exhibits a crystallographic mirror plane that is perpendicular to the ring and bisects the sulfamoyl and thiophosphate ester groups. In the crystal, molecules are linked by N—H⋯O hydrogen-bonding interactions reminiscent of carboxylic acid hydrogen bonding pairs, forming chains parallel to the b-axis direction.

Existence of intermolecular carboxylic acid-like hydrogen bonding is observed between inversion-related H1 and O3 pairs ( Fig. 2, Table 1) resulting in the formation of chains parallel to the b axis. This hydrogen bonding may also contribute to the observed pyramidal shape on the nitrogen. Though Cythioate has a structure similar to that of Famphur (O,O-dimethyl O-[p-[(N,N-dimethylsulfamoyl)phenyl] phosphorothioate; Baughman, 1997), the differences cannot be ignored as they may be the cause of differences in toxicity/activity. The Cythioate molecule exhibits a mirror plane that is perpendicular to the ring and bisects the sulfamoyl and thiophosphate groups. The presence of this mirror and the absence of one in Famphur result from most of the differences in overall molecular shape as well as specific differences.
Between Cythioate and Famphur a 70 σ difference in the O2-P-S1 bond angles, a 60 σ difference in the O2-P-O2a angles, and a 65 σ difference in O1-P-S1 bond angles are observed. This may be due to the distortion of the phosphorothioate group caused by the hydrogen bonding in Famphur. Interestingly, the P1-O1, P1-O2, and P1-S1 bond lengths are within 3 σ of each other.

Experimental
Crystals were grown by slow evaporation of a solution in EtOH.
In the final stages of refinement, two reflections with very small or negative F o 's were deemed to be in high disagreement with their F c 's and were eliminated from final refinement.

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 cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(F 2 ) is used only for calculating R-factors(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.