The structure of N,N',N"-tribenzylphosphorothioic triamide, C21H24N3PS, (I), and analysis of the bond-angle sums at the N atoms for this compound, and for 74 structures with a P(S)[N]3 skeleton and the N atom in a three-coordinate geometry found in the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53, 662–671], are reported. For (I), the bond-angle sum at one of the N atoms [359 (1)°] shows a nearly planar configuration, while the other two show a nonplanar geometry with bond-angle sums of 342 (1) and 347 (1)°. The location of the atoms attached to the nonplanar N atoms suggests an anti orientation of the corresponding lone electron pairs (LEPs) on these N atoms with respect to the P═S group. For 74 structures with a P(S)[N]3 skeleton and with the N atom in a three-coordinate geometry, the bond-angle sums at the N atoms were found to be in the range 293–360°. Among 307 such threecoordinate N atoms, 39% (120 N atoms) have bond-angle sums in the range 359–360°, in accordance with sp2 hybridization, and 45% (138 N atoms) have bond-angle sums in the range 352–359°, with hybridization close to sp2. For the orientation of the LEP with respect to the P═S group, the anti orientation was found to be a general rule for N atoms, with the corresponding bond-angle sums deviating by more than 8° from the planar value of 360°. In the title structure, the S atom takes part in intermolecular (N—H…)(N—H…)S hydrogen bonds, connecting the molecules into extended chains parallel to the b axis. The cooperation of one N atom in an N—H…S hydrogen bond as an H-atom donor, and in an N—H…N hydrogen bond as an acceptor, is a novel feature of the crystal structure.

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