Phosphorus-31 chemical shifts

The first phosphorane (74) with a a"phosphorus-silicon bond has been prepared (albeit in low, 20%,yield) by the reaction of (72) with bis(trimethylsilyl)magnesium (73)99. It has an unusually high phosphorus chemical shift but no 2L ray data are, as yet, available. 

Another interesting point is to be presented in relation to chemical shift evaluations. From the directly-measured spin-rotation constant of POF3, diamagnetic and paramagnetic contributions to phosphorus chemical shifts were estimated (ca. +1000 and —640 p.p.m.). Extended to H3P04, which is the commonly accepted reference compound, this gives about 320 p.p.m. for the absolute 31P chemical shift.a999,9)... 

Solvent and temperature effects have been especially studied in simple compounds—white phosphorus,(1969 180) PH3, (1967>43> PFS, (1968,51) phosphorus acid, phosphines, phosphonium compounds etc. (1965> 39 1967,169 1968,155 1969,53) phosphorus chemical shifts or line-widths,... 

The phosphorus chemical shift observed for the arsenic derivative 5 P = 315 is in accordance with the monomeric structure (39). This, however, is not the case for that observed for the antimony derivative, P = 44.5. The mass spectrum of the latter confirms its dimeric structure (37). 

Attempts at correlating endocyclic phosphorus bond angles with the phosphorus chemical shifts and P-N bond distances with C1 NQR frequencies have been made [314]. It appears that for closely related compounds there exists a narrow relationship between chemical shifts and endocyclic phosphorus angles [96, 358]. No generalized trend has yet emerged. The differences in the P-Cl bond lengths in PCl2 and PRCl units have been correlated with the C1 NQR frequencies [314],... 

A similar relationship between phosphorus chemical shifts and O-P-O bond angles in phosphate esters has been reported by Gorenstein, D. G. J. Am. Chem. Soc. 1975, 97, 898-900. 

The nickel chloride complex(X) of the spiro-cyclic phosphazene(V) is diamagnetic suggesting a square planar coordination around nickel. The P=N stretching vibration for the complex appears as two split bands(1215 and 1183 cm-1) compared to a single band at 1200 cm-1 observed for the ligand. The phosphorus chemical shifts move upfield compared to those of the ligand the spiro phosphorus atom is the one most affected [complex SpR 21.9 Sp(spir0) 25.5 ... 

X-ray crystallographic studies reveal that both ring protonation and complexation affect the phospha-zene in a similar way but the effect of protonation is more pronounced(1). For the hydrochloride adducts of amino icyclophospEazenes), the proton NMR shifts move downfield whereas phosphorus chemical shifts are markedly upfield to those observed for the free bases. The ring P = N stretching frequency also undergoes an upward shift for the hydrochloride adducts(l). 

There exists a fairly large amount of experimental data on the 31P chemical shift of molecules dissolved in isotropic phases. However, one is still far from having a good rationale of the different factors which may influence the phosphorus chemical shift. The same is true for the other nuclei which may be studied by n.m.r. 

M. Gee, R. E. Wasylishen, K. Eichele and J. F. Britten, Phosphorus chemical shift tensors for tetramethyldiphosphine a 31P single-crystal NMR, dipolar-chemical shift NMR and ab initio molecular orbital study.. Phys. Chem. A, 2000,104,4598-4605. 

Phosphorus chemical shift in CH2CI2 relative to 85 % H3PO4. 

I mentioned this in my chapter in Annual Review. That was when I found the isotopic shift due to on the NMR phosphorus chemical shifts of ATP because I had come full circle. I was now showing an isotopic mass effect in a spectroscopic parameter and that s where I started in my graduate work. It isn t a very important finding, but it gave me great pleasure to discover yet another effect of isotopic mass of a stable isotope with a spectroscopic manifestation. 

Phosphorus chemical shift and spin-spin coupling P-P tensors have been determined by Gee et al for tetramethyldiphosphine disulfide. 

Phosphorus chemical shift values are given in ppm with 85 % as external standard... 

In Fig. 2.4 we can follow the trend throughout the phosphorus chemical shift range. At the upheld end, white phosphorus resonates at < p= 88ppm. This is readily explained by an electron rich cluster structure with P-P-P angles of 60°. Coordination to a transition metal causes a reduction in electron density on phosphorus, as a P lone pair is used to create a donor bond. Similarly, substitution of a phosphorus atom by an isolobal transition metal fragment causes a downfield shift, as electron density is transferred from the electron rich phosphorus atoms to the poorer transition metal. 

From C- and H-NMR spectroscopy, we know that alkyl substitution on phenyl rings results in an upheld shift of the remaining C-H resonances. Phosphorus chemical shifts behave differently. Alkyl substituents have a - I effect on phosphorus. The phosphorus resonance is shifted downheld upon increasing alkyl subshtuhon (see Table 2.1). Phenyl substituents cause an upheld shift compared to respechve alkylated phosphorus compounds. PPhj has a chemical shift of < p=-6ppm, whereas PCyj has one of <5 p=9ppm. In addition, phosphorus chemical shifts are influenced by changes in the Tolman cone angle. 

A summary of phosphorus chemical shifts for phosphanes is given in Table 2.2, and a graphical display in Fig. 2.5. Both clearly illustrate the downheld shift of the... 

Table Z2 The dependence of phosphane phosphorus chemical shifts on the number of hydrogen ...

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