The double H-atom acceptability of the P=O group in new X P(O)(NHCH2C6H4-2-Cl)2 phosphoramidates [X = C6H5O- and CF3C(O)NH-]: a database analysis of compounds having a P(O)(NHR ) group
| Authors | |
|---|---|
| Year of publication | 2012 |
| Type | Article in Periodical |
| Magazine / Source | Acta Crystallographica Section C: Crystal Structure Communications |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1107/S0108270111052097 |
| Doi | http://dx.doi.org/10.1107/S0108270111052097 |
| Field | Inorganic chemistry |
| Keywords | phenyl bis(2-chlorobenzylamido)phosphinate; crystal structures |
| Description | In the hydrogen-bond patterns of phenyl bis(2-chlorobenzylamido)phosphinate, C20H19Cl2N2O2P, (I), and N,N'-bis(2-chlorobenzyl)-N''-(2,2,2-trifluoroacetyl)phosphoric triamide, C16H15Cl2F3N3O2P, (II), the O atoms of the related phosphoryl groups act as double H-atom acceptors, so that the P=O(H-N)2 hydrogen bond in (I) and the P=O(H-Namide)2 and C=OH-NC(O)NHP(O) hydrogen bonds in (II) are responsible for the aggregation of the molecules in the crystal packing. The presence of a double H-atom acceptor centre is a result of the involvement of a greater number of H-atom donor sites with a smaller number of H-atom acceptor sites in the hydrogen-bonding interactions. This article also reviews structures having a P(O)NH group, with the aim of finding similar three-centre hydrogen bonds in the packing of phosphoramidate compounds. This analysis shows that the factors affecting the preference of the above-mentioned O atom to act as a double H-atom acceptor are: (i) a higher number of H-atom donor sites relative to H-atom acceptor centres in molecules with P(=O)(NH)3, (N)P(=O)(NH)2, C(=O)NHP(=O)(NH)2 and (NH)2P(=O)OP(=O)(NH)2 groups, and (ii) the remarkable H-atom acceptability of this atom relative to the other acceptor centre(s) in molecules containing an OP(=O)(NH)2 group, with the explanation that the N atom bound to the P atom in almost all of the structures found does not take part in hydrogen bonding as an acceptor. Moreover, the differences in the H-atom acceptability of the phosphoryl O atom relative to the O atom of the alkoxy or phenoxy groups in amidophosphoric acid esters may be illustrated by considering the molecular packing of compounds having (O)2P(=O)(NH) and (O)P(=O)(NH)(N)groups, in which the unique N-H unit in the above-mentioned molecules almost always selects the phosphoryl O atom as a partner in forming hydrogen-bond interactions. |
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