Evidence of Long-Range ₁₃C-₃₁P Couplings: A ₁₃C NMR Investigation of Some Aryl Esters of Phosphor-Amidochloridic Acid and the Related Compounds

Abstract

In ¹³ NMR study organophosphorus compounds, sign and magnitude of ¹³ C-³¹ P spin-spin couplings has been of great interest to elucidate stereochemistry and electronic state of phosphorus central atom. However, a discussion about the mechanisms of carbon-phosphorus couplings is still complicated specially in the case of long-range couplings that also are not frequently observed. In this study, ¹³ C NMR chemical shifts and coupling constants have been determined for a series of aryl esters of phosphoramidochloridic acid with the general formula: R₂NP(O)(OAr)Cl, in which R = methyl and/or benzyl, Ar = p-tolyl. p-nitrophenyl, and phenyl. Besides usual W-couplings that could be found in these systems, we detected long-range couplings through five and six bonds. It has been shown that, these couplings are highly dependent on substituents on phosphorus nuclei. The data for some related compounds have been also obtained for a comparison.