Phosphonic acids and esters–XVIII

Dependence of the long‐range phosphorus–hydrogen coupling constant nJP–H (n = 3,6,7) on the bond order between phosphorus and its substituents: preparation and spectroscopic characterization of several phosphoramidates

“…2 Griffin, 3 Stothers and Robinson 4 and Berry et al 5 have reported the correlation between the hybridization state of the phosphorus atom with proton shift and spin-spin coupling constant J P -H , which was interpreted by Hendrickson et al 6 The influence of benzene on the 1 H NMR spectra of mononuclear phosphorus(V) amides and dimethylamino cyclotriphosphazatrienes is described by Keat and Shaw. 7 Several other publications have described the short-and long-range J P -H in phosphorus compounds 3 -22 and four-and five-bond coupling constants ( 4 J P -H , 5 J P -H ) in allylic and homoallylic phosphorus compounds. 11,13,14,19,22 The observations of five, six, and seven bond couplings in isomeric methylbenzylphosphonium salts have been reported by Khaleeludin and Scott 15 and Gordon and Griffin 14,16 and some other studies have reported 3 J P -H spin-spin coupling too. 6,16 In the above-mentioned studies, several models have been put forward to explain the mechanism of long-range Ł Correspondence to: K. Gholivand, Department of Chemistry, Tarbiat Modarres University, PO Box 14155-4838, Tehran, Iran.…”

New organotin(IV) complexes of nicotinamide, isonicotinamide and some of their novel phosphoric triamide derivatives: Syntheses, spectroscopic study and crystal structures

“…As it can be seen from Table 1, chemical shift of 31 P for compounds L 1 -L 4 is in the range of 2.18-7.08 ppm. 31 PNMR spectra indicate that by coordinating to Sn, this parameter shows a small shift (at most 1.5 ppm) to up fields. 1 H NMR spectra showed that 2 J(PNH) amide is observed only for L 4 and its Sn complex C 4 .…”

“…Such interesting couplings have been observed only in few compounds up to now [30][31][32][33][34][35][36]. Different explanations have been presented in some articles to describe appearing or disappearing of P-H long-range couplings; such as Fermi contact interactions [34], stereochemical and structural effects [30][31][32][33], ''ground-state hyperconjugation" or ''r-p configuration interactions" [35], angular overlap model [35] and partial multiple bonds formation [30]. 1 H NMR spectra of molecules C 1 -C 6 showed the Sn(IV) satellites with 2 J( 119 Sn, H) in the range of 71.…”

Analogs of phosphoenolpyruvate. Specificity of pyruvate kinase from rabbit muscle

“…This indicates that a hydrolysis mechanism involving acid catalysis as well as neighboring group participation (Clark and Kirby, 1963), pentacovalent phosphorus intermediates and pseudorotational conversions (Benkovic and Shray, 1969) may be operating. 4 In contrast to the reliability of stereochemical assignments made on the basis of assuming / -(trans) being greater than |j| aipccni (cis) (Kenyon and Westheimer, 1966;Martin et a!., 1967), the generalization does not hold if the ;i!P nucleus is not directly attached to one of the carbons of the double bond (Cohn et alt 1970). For example, for phosphoenolpyruvate |/¡3ipoccin (trans) > |/|i3pocciH (cis), but for both the (£)-and (Z)-methyl 3-(dimethoxyphosphinyloxy)crotonates and the [£]-and (Z)-trimethyl phosphoenol-a-kctobutyrates |/|3ipocc>H…”