Different cyclic motifs in phosphoric triamides containing a C(O)NHP(O)(NH)
In the crystal networks of N,N′‐bis(2‐chlorobenzyl)‐N′′‐(2,6‐difluorobenzoyl)phosphoric triamide, C21H18Cl2F2N3O2P, (I), N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis(4‐methoxybenzyl)phosphoric triamide, C23H24F2N3O4P, (II), and N‐(2‐chloro‐2,2‐difluoroacetyl)‐N′,N′′‐bis(4‐methylphenyl)phosphoric triamide, C16H17ClF2N3O2P, (III), C=O...H—NC(O)NHP(O) and P=O...H—Namide hydrogen bonds are responsible for the aggregation of the molecules. This is the opposite result from that commonly observed for carbacylamidophosphates, which show a tendency for the phosphoryl group, rather than the carbonyl counterpart, to form hydrogen bonds with the NH group of the C(O)NHP(O) skeleton. This hydrogen‐bond pattern leads to cyclic R 2 2(10) motifs in (I)–(III), different from those found for all previously reported compounds of the general formula RC(O)NHP(O)[NR 1 R 2]2 with the syn orientation of P=O versus NH [R 2 2(8)], and also from those commonly observed for RC(O)NHP(O)[NHR 1]2 [a sequence of alternate R 2 2(8) and R 2 2(12) motifs]. In these cases, the R 2 2(8) and R 2 2(12) graph sets are formed through similar kinds of hydrogen bond, i.e. a pair of P=O...H—NC(O)NHP(O) hydrogen bonds for the former and two C=O...H—Namide hydrogen bonds for the latter. This article also reviews 102 similar structures deposited in the Cambridge Structural Database and with the International Union of Crystallography, with the aim of comparing hydrogen‐bond strengths in the above‐mentioned cyclic motifs. This analysis shows that the strongest N—H...O hydrogen bonds exist in the R 2 2(8) rings of some molecules. The phosphoryl and carbonyl groups in each of compounds (I)–(III) are anti with respect to each other and the P atoms are in a tetrahedral coordination environment. In the crystal structures, adjacent molecules are linked via the above‐mentioned hydrogen bonds in a linear arrangement, parallel to  for (I) and (III) and parallel to  for (II). Formation of the NC(O)NHP(O)—H...O=C instead of the NC(O)NHP(O)—H...O=P hydrogen bond is reflected in the higher NC(O)NHP(O)—H vibrational frequencies for these molecules compared with previously reported analogous compounds.
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Document Type: Research Article
Publication date: July 15, 2011