Different cyclic motifs in phosphoric triamides containing a C(O)NHP(O)(NH)2skeleton and anR22(10) graph set in three new compounds: a database analysis of hydrogen-bond strengths based on motifs

Abstract

In the crystal networks of N,N'-bis(2-chlorobenzyl)-N''-(2,6-difluorobenzoyl)phosphoric triamide, C(21)H(18)Cl(2)F(2)N(3)O(2)P, (I), N-(2,6-difluorobenzoyl)-N',N''-bis(4-methoxybenzyl)phosphoric triamide, C(23)H(24)F(2)N(3)O(4)P, (II), and N-(2-chloro-2,2-difluoroacetyl)-N',N''-bis(4-methylphenyl)phosphoric triamide, C(16)H(17)ClF(2)N(3)O(2)P, (III), C=O···H-N(C(O)NHP(O)) and P=O···H-N(amide) 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-N(C(O)NHP(O)) hydrogen bonds for the former and two C=O···H-N(amide) 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 [010] for (I) and (III) and parallel to [100] for (II). Formation of the N(C(O)NHP(O))-H···O=C instead of the N(C(O)NHP(O))-H···O=P hydrogen bond is reflected in the higher N(C(O)NHP(O))-H vibrational frequencies for these molecules compared with previously reported analogous compounds.