Phosphoric triamides have extensive applications in biochemistry and are also used as O-donor ligands. Four new mixed-amide phosphoric triamide structures, namely rac-N-tert-butyl-N',N"-dicyclohexyl-N"-methylphosphoric triamide, C17H36N3OP, (I), rac-N,N'-dicyclohexyl-N'-methyl-N"-(p-tolyl)phosphoric triamide, C20H34N3OP, (II), N,N',N"-tricyclohexyl-N"-methylphosphoric triamide, C19H38N3OP, (III), and 2-[cyclohexyl(methyl)amino]-5,5-dimethyl-1,3,2λ5-diazaphosphinan-2-one, C12H26N3OP, (IV), have been synthesized and studied by X-ray diffraction and spectroscopic methods. Structures (I) and (II) are the first diffraction studies of acyclic racemic mixed-amide phosphoric triamides. The P—N bonds resulting from the different substituent –N(CH3)(C6H11), (C6H11)NH–, 4-CH3-C6H4NH–, (tert-C4H9)NH– and –NHCH2C(CH3)2CH2NH– groups are compared, along with the different molecular volumes and electron-donor strengths. In all four structures, the molecules form extended chains through N—H…O hydrogen bonds.

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