Polymorphism for a novel phosphoramidate; NMR and X-ray crystallography
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- Gholivand, K., Afshar, F., Shariatinia, Z. et al. Struct Chem (2010) 21: 629. doi:10.1007/s11224-010-9592-z
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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 2J(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.