Original Research

Structural Chemistry

, Volume 21, Issue 3, pp 629-636

Polymorphism for a novel phosphoramidate; NMR and X-ray crystallography

  • Khodayar GholivandAffiliated withDepartment of Chemistry, Tarbiat Modares University Email author 
  • , Farzaneh AfsharAffiliated withDepartment of Biology, Islamic Azad University
  • , Zahra ShariatiniaAffiliated withDepartment of Chemistry, Amirkabir University of Technology
  • , Karim ZareAffiliated withDepartment of Chemistry, Science and Research Branch, Islamic Azad University (IAU)Department of Chemistry, Shahid Beheshty University

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Abstract

New phosphoramidates with formula 3-NC5H4C(O)NHP(O)XY (X=Y=Cl (1), X=Y=NH–C(CH3)3 (2a,2b), X=Y=N(C4H9)2 (3), X=Cl, Y=N(C2H5)2 (4) were synthesized and characterized by IR, 1H-, 13C-, 31P-NMR spectroscopy and CHN elemental analysis. Surprisingly, the reaction of compound 2a with LaCl3, 7H2O in 3:1 M ratio leads to a polymorph of this compound (2b). NMR spectra indicate that 2 J(PNHamide) in 2b (7.0 Hz) is very much greater than in 2a (4.1 Hz), while δ(31P) values are identical for both of them. In IR spectra, υ(P=O) is weaker but υ(C=O) is stronger in 2a than in 2b. The structures of 2a, 2b were determined by X-ray crystallography. These compounds form centrosymmetric dimers via two intermolecular P=O……H–N hydrogen bonds. Strong intermolecular N–H…N, N–H…O and weak C–H…O hydrogen bonds lead to a three-dimensional polymeric cluster in the 2a while intermolecular strong N–H……N and weak C–H……O hydrogen bonds form a two-dimensional polymeric chain in 2b.

Graphical Abstract

New phosphoramidates were synthesized and characterized by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis. Surprisingly, the crystal structures of two polymorph compounds were determined using X-ray crystallography. These compounds have differences in their IR and NMR spectra as well as in their crystal structures. They form polymeric chains via intermolecular hydrogen bonds.
http://static-content.springer.com/image/art%3A10.1007%2Fs11224-010-9592-z/MediaObjects/11224_2010_9592_Figa_HTML.jpg

Keywords

Phosphoramidates NMR X-ray crystallography Hydrogen bonds Polymorphism