Synthesis and Spectroscopic characterization of a new phosphoric triamide; [2,3-F2–C6H3C(O)NH]P(O)[N(CH3)(C6H11)]2 as an example of a compound with a second-order 13C NMR spectrum

Phosphoramids are suitable compounds for demonstrating the high capability of NMR spectroscopy in characterizing newly synthesized compounds [1-3]. In this study, we synthesized a new phosphoric triamide with formula [2,3-F2–C6H3C(O)NH]P(O)[N(CH3)(C6H11)]2 (1) and characterized by 1H, 13C{1H}, 31P{1H} NMR and IR spectroscopy. The 31P{1H} NMR spectrum of this compound represents a singlet at chemical shift 25.01 ppm (Fig. 1) which indicates that the synthesized compound is pure. In the 13C NMR spectrum of 1, both two- and three-bond distance couplings with the phosphorus atom [2J(P,C) and 3J(P,C), respectively] is observed for corresponding carbon atoms of cyclohexyl rings and as expected, 2J(P,C) = 4.6 Hz is greater than 3J(P,C) = 1.7 and 3.6 Hz [i.e. 2J(P,C) > 3J(P,C)]. As shown in the experimental 13C NMR spectrum in Fig. 2, the unsubstituted carbon atoms of the 2,3-F2–C6H3– fragment (C-4, C-5 and C-6) give the second-order spectra that are attributed to the coupling with two fluorine atoms. Among these carbons, the carbon ortho to the fluorine (C-4) appears upfield which can be confirmed by comparing the predicted spectrum, calculated by the MestReNova software (Mnova) [4], and the experimental spectrum (Fig. 2). As Mnova failed to calculate the splitting for compound 1, only the chemical shift information was used for building predicted spectrum. Hence, only singlet peaks are observed in the predicted spectrum.