P chemical shifts

The rates of hydrolysis of a variety of cyclic and acyclic phosphonium salts do not correlate with their P chemical shifts. ... 

P chemical shift (8) relative to external 85% H3P04. b The designations (b) and (t) refer to bridging and terminal phosphido atoms. 

P Chemical Shifts of (HI) and pKa Values of the Conjugate Acids of Amines... 

So, this fact is strong evidence in favor of the intra- and inter-molecular dative P—B bond in 126. In solution, 126 is easily oxidized and undergoes addition reactions with sulfur and selenium, with the formation of the corresponding oxide (166), sulfide (167), or selenide (168) [Eq. (129)]. The 3,P chemical shifts of other compounds (166) (27 ppm), (167) (47 ppm), and (168) (46 ppm) are close to that observed for their structural analogues. These data and the values of dipole moments of 4,3 and 4,5 D for 166 and 167, respectively, make it possible to exclude the formation of intramolecular dative P—B bonds similar to those observed for borylphosphine ethene... 

More comprehensive P n.m.r. studies of a range of noble metal phosphine complexes, including mer-[RhCl3L3] (L = wide choice of tertiary phosphine), have shown a correlation between the P chemical shift of the free phosphine and the change in chemical shift on co-ordination. The effect of changing the halide ligand on the P chemical shift was also studied. 

A specific example can be found in the Rh-chemistry mentioned in connection with Figure 1.4. The complex RhPh(PPh3)(Binap), 11, shows very different J( P. P) values with the trans-interaction much larger than the cis. Taken together, the three different P chemical shifts and the various j( Rh, P) and J( P, P) values are all important indicators of the correct structure for this complex. 

J. J. Potwarka, D. J. Drost, P. C. Williamson, T. Carr, G. Canaran, W. J. Rylett and R. W. A. Neufeld, H-decoupled P chemical shift imaging study of medicated schizophrenic patients and healthy controls. Biol. Psychiatry, 1999, 45,687-693. 

H. P. Volz, S. Riehemann 1. Maurer, et ah. Reduced phosphodiesters and high-energy phosphates in the frontal lobe of schizophrenic patients a (31)P chemical shift spectroscopic-imaging study. Biol. Psychiatry, 2000,47,954—961. 

Table 30). The chemical shift of the P signals depends closely upon the electronegativity of the 1.1-substituents. A relationship beetween the P-chemical shift and the long-wave absorption has also been established (see p. 103). 

The same situation is encountered with a,/ -alkynic phosphonium salts in which C(a) carbons are strongly shielded vs C p) carbons 47.8-73.0 vs 119-127 ppm36,97. The linear correlation of the C(a) and C(P) chemical shifts with a para Hammet constant was illustrative of the polarization of the 7r-electron system in the C=C triple bond (Figure 8). In the same sense, the observed C(flt) and C(/J) chemical shifts were used to argue for the existence of either resonance hybrid structures as in the case of enaminophosphonium salts98,99 or incipient ylide contribution40. 

FIGURE 8. Correlation of the C(a) and C(P) chemical shifts with opara in (C6H5)3P+C(a)= Cmp-C6 H4R97... 

Table I P Chemical shifts (ppm from H3PO4) and spin cou-...

Evolution of multiple quantum coherence (of order p) is treated as successive evolution of each of the p chemical shifts. As expected, double quantum coherence precesses at wt + cos, and zero quantum coherence precesses at (i)j — 0)s. As we noted in Section 11.5, such coherences are not affected by spin coupling. 

A selection of AN values has already been given in Table 2-5 of Section 2.2.6 cf. also Table 6-6 in Section 6.5.1. The observed solvent-dependent P chemical shifts result mainly from the polarization of the dipolar P=0 group, induced by the interaction with electrophilic solvents A, particularly HBD solvents. The decrease in electron density at the phosphorus atom results in a deshielding proportional to the strength of the probe/solvent interaction. In solutions of protic acids, the P chemical shift of the 0-protonated triethyl hydroxyphosphonium salt is observed. Since Et3PO is very hygroscopic and therefore not very suitable from an experimental point of view, the use of (n-Bu)3PO instead of Et3PO as probe molecule has been recommended [250]. 

P NMR chemical shift data have been used extensively to confirm double bond formation in phosphaarsenes and diphosphenes. The P chemical shift range for these compounds is typically from -1-500 to -1-700 ppm (85% H3PO4). The shifts are among the lowest known in P NMR. P NMR chemical shifts for phosphinoarsines are similar to those for diphosphines and aminophosphines. ... 

The isotropic "P chemical shifts move to high-field values with increasing connectivity of phosphate tefrahedra and increasing charge on the coordinated cations. For orthophosphates and one-, two- and three-connected... 

Figure 2. Comparison of P 2p binding energies from XPS and P chemical shifts from NMR.

Figure 7.4. Pictorial representation of the P chemical shift ranges for various classes of phosphorus atom.s. Chemical shifts are referred to 85% H3PO4.

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