In N,N,N',N'-tetraethyl-N"-(4-fluorobenzoyl)phosphoric triamide, C15H25FN3O2P, (I), and N-(2,6-difluorobenzoyl)-N',N"-bis(4-methylpiperidin-1-yl)phosphoric triamide, C19H28F2N3O2P, (II), the C—N—C angle at each tertiary N atom is significantly smaller than the two P—N—C angles. For the other new structure, N,N'-dicyclohexyl-N"-(2-fluorobenzoyl)-N,N'-dimethylphosphoric triamide, C21H33FN3O2P, (III), one C—N—C angle [117.08 (12)°] has a greater value than the related P—N—C angle [115.59 (9)°] at the same N atom. Furthermore, for most of the analogous structures with a [C(═O)NH]P(═O)[N(C)(C)]2 skeleton deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B58, 380–388], the C—N—C angle is significantly smaller than the two P—N—C angles; exceptions were found for four structures with the N-methylcyclohexylamide substituent, similar to (III), one structure with the seven-membered cyclic amide azepan-1-yl substituent and one structure with an N-methylbenzylamide substituent. The asymmetric units of (I), (II) and (III) contain one molecule, and in the crystal structures, adjacent molecules are linked via pairs of N—H…O═P hydrogen bonds to form dimers.

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