¹³C n.m.r. spectroscopy of diethyl alkyl‐ and benzyl‐phosphonates. A study of phosphorus–carbon spin–spin coupling constants over one to seven bonds

Abstract

C chemical shifts and 31P-13C spin-spin coupling constants are reported for 10 akyl-, 20 benzyl-and 3 (naphthylmethy1)-phosphonates. While in saturated aliphatic chains P-C couplings over more than four bonds cannot be resolved, couplings over up to seven bonds are observed in the benzyl type systems. Conformational and substituent effects on J(PC) are studied and discussed. "J(PF) (n = 4,5,6) are reported for the isomeric (fluorobenzy1)phosphonates and "J(PP) (n = 5,6,7) were obtained from the "C satellites in the 3'P n.m.r. spectra of the isomeric diphosphonates, C,H,[CH,P(O)(OEt),],. Comparison of those l3c absorptions of the latter, which represent the X parts of ABX or AA'X spin systems, with the spectra of the corresponding (methylbenzyl)phosphonates, CHjC6H,CH2P(o)(oEt),, yielded the relative signs of "J(Pc) (n = 2-6). a Coupling constants in Hz b0.2 Hz); only magnitudes given. Measured splittings corrected by +0.1 Hz according to Ref. 41. Couplings to isopropyl carbons not resolved. J(FC) are 15.6(C-11, 245.

Examination of P−OR Bridging Bond Orders in Phosphate Monoesters using18O Isotope Shifts in31P NMR

“…This two-bond coupling constant reflects the P−O−C interaction, not solely the P−O bond. Previously published data show that two-bond phosphorus−carbon coupling constants depend on the hybridization of the carbon atom, with sp 2 carbons exhibiting slightly higher coupling constants than sp 3 carbon atoms. , We obtained similar results; the P−O−C coupling constant is 4.8 Hz in methyl phosphate, 6.0 Hz in phenyl phosphate, and 5.8 Hz in p -nitrophenyl phosphate. The differences between these coupling constants for alkyl versus aryl phosphate esters may be explained by the aid of Jameson's s-character theory .…”

The Syntheses and Characterization of New Dithiophosphonates derived from Novel 2,4-Bis(methoxytolyl)-1,3-dithia-2,4-diphosphetane 2,4- disulfides and Their Ni(II) Complexes

“…As a general trend, the 13 C NMR signals of all the complexes show up at higher fields relative to the corresponding signals in the spectra of the ligands. Similar trends were reported for structurally related compounds (26)(27)(28)(29)(30)(31)(32).…”

Alkaline Earth Metal–Organic Frameworks with Tailorable Ion Release: A Path for Supporting Biomineralization

“…Analysis of the NMR spectra reveals how the bisphosphonate ligands are affected in the series of materials SrPAEM, SrCaPAEM, and CaPAEM. The 13 C CP MAS NMR spectra confirm that the ethyl functional groups (observed at 16 and 62 ppm; Figure S3) in the tetraethyl-PXBP ligands are hydrolyzed (i.e., no resonances are observed for the ethyl groups) during the hydrothermal synthesis of these compounds . On looking at CaPAEM, SrPAEM, and SrCaPAEM, the isotropic chemical shifts (δ iso ) for the ortho-methylene bridging C atoms appear at ∼35 ppm, and those for the three unique aromatic C atoms are located between 130 and 135 ppm (Figures b and S3).…”

“…The 13 C CP MAS NMR spectra confirm that the ethyl functional groups (observed at 16 and 62 ppm; Figure S3) in the tetraethyl-PXBP ligands are hydrolyzed (i.e., no resonances are observed for the ethyl groups) during the hydrothermal synthesis of these compounds. 32 On looking at CaPAEM, SrPAEM, and SrCaPAEM, the isotropic chemical shifts (δ iso ) for the orthomethylene bridging C atoms appear at ∼35 ppm, and those for the three unique aromatic C atoms are located between 130 and 135 ppm (Figures 1b and S3). Substitution of Ca for Sr impacts the aromatic 13 C resonances, where the methine (−CH; δ iso ( 13 C) ≈ 135 ppm) carbon shifts to lower frequency, whereas the lowest frequency aromatic 13 C resonance [δ iso ( 13 C) ≈ 130 ppm] shifts to higher frequency, decreasing the resolution between the C2, C3, and C4 resonances (Figure 1b).…”