A new Z′=(2+0.5+0.5) amidophosphoester structure: Hirshfeld surface analysis of symmetry-independent molecules

Abstract

Abstract Tetraethyl 1,3-phenylenebis(phosphoramidate) was synthesized and characterized by 1H, 13C, 31P NMR, IR and mass spectroscopies. The asymmetric unit is composed of two half-molecules, each residing on a two-fold axis, and two complete molecules, thus leading to a Z′=(2+0.5+0.5)=3 structure. The most plausible explanation for the occurrence of multiple independent molecules is a frustration between relatively strong hydrogen bond interactions and weaker CH···π interactions. In each of the molecules, the P atoms are in a similar distorted tetrahedral environment. The N atoms bonded to P atoms have mainly sp2 character tending towards a planar environment. In the crystal structure, the phosphoryl O atoms are involved in classical N–H···O=P and weaker C–H···O=P hydrogen bonds as (N–H)(C–H) ···O=P, acting as a double hydrogen-bond acceptor. These hydrogen bonds along with other C–H···O hydrogen bonds and C–H···π interactions create a 3D crystalline network. Hirshfeld surfaces and two-dimensional (2D) fingerprint plots are calculated for analyzing intermolecular interactions in each of the independent molecules of the title compound. For all four independent molecules, the contribution of H···H contacts to the total interactions is decisive, being larger than 60% for each molecule. The O···H/H···O contacts are the characteristic intermolecular contacts in the corresponding molecules. Furthermore, the C···H/H···C, including the C–H···π interactions, and N···H/H···N contacts cover other intermolecular contacts in the crystal lattice.