Analysis of P–O–C, P–S–C and P–O–P angles: a database survey completed with four new X-ray crystal structures

Conformational flexibility in amidophosphoesters: a CSD analysis completed with two new crystal structures of (C6H5O)2P(O)X [X = NHC7H13 and N(CH2C6H5)2]

The crystal structures of diphenyl (cycloheptylamido)phosphate, C19H24NO3P or (C6H5O)2P(O)(NHC7H13), (I), and diphenyl (dibenzylamido)phosphate, C26H24NO3P or (C6H5O)2P(O)[N(CH2C6H5)2], (II), are reported. The NHC7H13 group in (I) provides two significant hydrogen-donor sites in N—H...O and C—H...O hydrogen bonds, needed for a one-dimensional hydrogen-bond pattern along [100] in the crystal, while (II), with a (C6H5CH2)2N moiety, lacks these hydrogen bonds, but its three-dimensional supramolecular structure is mediated by C—H...π interactions. The conformational behaviour of the phenyl rings in (I), (II) and analogous structures from the Cambridge Structural Database (CSD) were studied in terms of flexibility, volume of the other group attached to phosphorus and packing forces. From this study, synclinal (±sc), anticlinal (±ac) and antiperiplanar (±ap) conformations were found to occur. In the structure of (II), there is an intramolecular C ortho —H...O interaction that imposes a +sc conformation for the phenyl ring involved. For the structures from the CSD, the +sc and ±ap conformations appear to be mainly imposed by similar C ortho —H...O intramolecular interactions. The large contribution of the C...H/H...C contacts (32.3%) in the two-dimensional fingerprint plots of (II) is a result of the C—H...π interactions. The differential scanning calorimetry (DSC) analyses exhibit peak temperatures (T m) at 109 and 81 °C for (I) and (II), respectively, which agree with the strengths of the intermolecular contacts and the melting points.

Dicyclohexylammonium O,O’-Diphenyl Phosphate, [(C6H11)2NH2][(C6H5O)2P(O)(O)]: Spectroscopic Study, Crystal Structure, and Hirshfeld Surface Analysis

The title salt, [(C6H11)2NH2][(C6H5O)2P(O)(O)], crystallizes in the chiral space group P212121, composed of achiral cation and anion components. The strong charge-assisted N–H…O hydrogen bonds build a linear assembly along the a axis, including a non-centrosymmetric C22(6) chain graph-set motif. The intra and intermolecular C–H…O interactions as well as the C–H…π-electron ring interactions also exist in the crystal structure. Fingerprint plots are used for a detailed investigation of intermolecular interactions participating in the crystal packing. The spectroscopic features (IR, 1H NMR, 13C{1H} NMR, 31P{1H} NMR, and mass) are studied.

Two single-enantiomer amidophosphoesters: a database study on the chirality of (O)2P(O)(N)-based structures

The crystal structures of two single-enantiomer amidophosphoesters with an (O)₂P(O)(N) skeleton, i.e. diphenyl [(R)-(+)-α-methylbenzylamido]phosphate, (I), and diphenyl [(S)-(-)-α-methylbenzylamido]phosphate, (II), both C₂₀H₂₀NO₃P, are reported. In both structures, chiral one-dimensional hydrogen-bonded architectures, along [010], are mediated by N-H...OP interactions. The statistically identical assemblies include the noncentrosymmetric graph-set motif C(4) and the compounds crystallize in the chiral space group P2₁. As a result of synergistic co-operation from C-H...O interactions, a two-dimensional superstructure is built including a noncentrosymmetric R₄⁴(22) hydrogen-bonded motif. A Cambridge Structural Database survey was performed on (O)₂P(O)(N)-based structures in order to review the frequency of space groups observed in this family of compounds; the hydrogen-bond motifs in structures with chiral space groups and the types of groups inducing chirality are discussed. The ^2,3J_X-P (X = H or C) coupling constants from the NMR spectra of (I) and (II) have been studied. In each compound, the two diastereotopic C₆H₅O groups are different, which is reflected in the different chemical shifts and some coupling constants.

Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation

The nano-composites Fe₃O₄@SiO₂@PTA(+) and Fe₃O₄@SiO₂@PTA(−) (PTA: phosphoric triamide) were prepared and used for the chiral separation of five racemic mixtures.

A combined X-ray crystallography and theoretical study of N-H...OX (X is =P and -C) hydrogen bonds in two new structures with a (C-O)2(N)P(=Y) (Y is O and S) skeleton

The crystal structures of N,N'-(cyclohexane-1,4-diyl)bis(O,O'-diphenylphosphoramide), C₃₀H₃₂N₂O₆P₂ or (C₆H₅O)₂P(O)(1-NH)(C₆H₁₀)(4-NH)P(O)(OC₆H₅)₂, (I), and N,N'-(1,4-phenylene)bis(O,O'-dimethylthiophosphoramide), C₁₀H₁₈N₂O₄P₂S₂ or (CH₃O)₂P(S)(1-NH)(C₆H₄)(4-NH)P(S)(OCH₃)₂, (II), have been investigated. In the structure of (I), with an (O)₂(N)P(O) skeleton, two symmetry-independent phosphoramide molecules are linked through N-H...O=P hydrogen bonds. In the structure of (II), with an (O)₂(N)P(S) skeleton, the ester O atoms take part in N-H...O-C hydrogen bonds as acceptors; the P=S groups do not participate in hydrogen-bonding interactions. The strengths of these hydrogen bonds were evaluated, using quantum chemical calculations with the GAUSSIAN09 software package at the B3LYP/6-311G(d,p) level of theory. For this, LP(O) to σ*(NH) charge transfers were studied, according to the second-order perturbation theory in natural bond orbital (NBO) methodology, for a three-component cluster of hydrogen-bonded molecules for both structures, including all of the independent N-H...O hydrogen bonds observed in the crystal packing. The details of the intermolecular interactions were studied by Hirshfeld surface maps and two-dimensional fingerprint plots.

Evaluation of N-H...S and N-H...π interactions in O,O'-diethyl N-(2,4,6-trimethylphenyl)thiophosphate: a combination of X-ray crystallographic and theoretical studies

In the crystal structure of O,O'-diethyl N-(2,4,6-trimethylphenyl)thiophosphate, C₁₃H₂₂NO₂PS, two symmetrically independent thiophosphoramide molecules are linked through N-H...S and N-H...π hydrogen bonds to form a noncentrosymmetric dimer, with Z' = 2. The strengths of the hydrogen bonds were evaluated using density functional theory (DFT) at the M06-2X level within the 6-311++G(d,p) basis set, and by considering the quantum theory of atoms in molecules (QTAIM). It was found that the N-H...S hydrogen bond is slightly stronger than the N-H...π hydrogen bond. This is reflected in differences between the calculated N-H stretching frequencies of the isolated molecules and the frequencies of the same N-H units involved in the different hydrogen bonds of the hydrogen-bonded dimer. For these hydrogen bonds, the corresponding charge transfers, i.e. lp (or π)→σ*, were studied, according to the second-order perturbation theory in natural bond orbital (NBO) methodology. Hirshfeld surface analysis was applied for a detailed investigation of all the contacts participating in the crystal packing.