Phosphorus-31 NMR spectra

The very sensitive 19F nucleus can be introduced into tRNAs by incorporation of 5-fluorouracil in place of uracil687 (Fig. 5-54A,B). Phosphorus 31 NMR spectra (Fig. 5-54C) can provide information about conformations of the chain.688... 

Complexes of the latter two types have been assigned seven-coordinate structures on the basis of their proton and phosphorus-31 NMR spectra even though the oxidation number of the iridium atom is 3+. 

Figure 9. Phosphorus-31 NMR spectra of solutions of (a) [U(ai-P2Wi70

When our studies commenced it had been assumed that the mechanism of asymmetric hydrogenation by chelating rhodium phosphine complexes followed a similar pathway. It has been demonstrated, however, that the timing is quite different, and that oxidative addition of hydrogen to metal does not occur in the initial stages of reaction. This conclusion follows from studies on the phosphorus-31 NMR spectra of hydrogenated complex solutions made separately by Halpern,... 

Figure 1. Rhodium enamide complexes derived from (a) bis-diphenylphosphiho-ethane and (b) DIP AMP with methyl z-a-benzamidocinnamate phosphorus-31 NMR spectra, MeOH, 25°C.

Figure 2. Regioselectivity in enamide complexation phosphorus-31 NMR spectra, MeOH, 25° C.

Physical Measurements. For the electrolyses, a Wenking potentiostat model 70TS1 and a Koslow Scientific coulometer model 541 were used. Voltammetry with wax-impregnated graphite and rotating platinum electrodes was performed as described elsewhere (7, 8). IR and electronic spectra were measured on Perkin-Elmer 225 and Cary 14 instruments. X-band ESR spectra were recorded at room temperature on a JEOL MES-3X spectrometer. Phosphorus-31 NMR spectra were recorded in the pulse mode on a Varian XL-100 instrument at 40.5 MHz using a deuterium lock, or on a Bruker HFX-90 instrument at 36.43 MHz using a fluorine lock. 

FIGURE 19-31 Fourier transform phosphorus-31 NMR spectra for ATP solution containing magnesium ions. The ratios on the right are moles of Mg to moles of ATP. (From J. W. Akitt, NMR and Chemistry, 2nd ed., p. 245, London Chapman Hall, 1983. With permission.)... 

Many of these nickel carbonyl-base compounds have been prepared primarily for use in infrared studies, some of the conclusions of which are summarized briefly in Section II, C 30,41,46,47,48,50,51,127,349). The phosphine-nickel complexes have catalytic activity in the polymerization of acetylenes, and the mechanisms of these polymerizations have been studied 350, 351). Interest in these catalysts has led to an investigation of their phosphorus-31 NMR spectra, which may be qualitatively correlated with the accepted ideas on metal-ligand bonding (72). 

It is possible to distinguish between phosphine complexes of platinum and rhodium by phosphorus-31 NMR spectroscopy, a technique not available to the early coordination chemists. Given that phosphorus-31 (100% abundant), platinum-195 (33% abundant), and rhodium-103 (100% abundant) all have nuclear spin quantum numbers of 1/2, sketch 31P NMR spectra of the following complexes (assume all protons are decoupled from the phosphorus nuclei) ... 

The solid and solution P-31 NMR spectra of the BPPM-rhodium complex are shown in Figure 6. The solution spectrum was obtained in acetone-d6 as the solvent, and displays an unusual coupling pattern when compared with the previously published spectrum obtained in methanol-d4 (II, 12). The spectrum shown in Figure 6 displays four sets of phosphorus signals two sets of four signals are centered at 43.5... 

The solution and solid P-31 NMR spectra of the prophos ligand are presented in Figure 10. As seen from this figure, the expected nonequivalence of the phosphorus atoms was observed in both spectra. The signals in the solid-state spectrum showed increased shielding relative to the solution spectrum. The solution spectrum also revealed a P-P coupling (/P P = 20.5 Hz). 

NMR Spectral Properties in Compound Characterisation and Structural Analysis VCH New York 1994. (c) Verkade, J. G Quin, L. D. Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis VCH Publishers Deerfield Beach, FL 1987. (d) Gorenstein, D. G Phosphorus-31 NMR Principles and Applications Academic Press Orlando, FL 1984. (e) NMR Spectra of Phosphorus Compounds, Topics in Phosphorus Chemistry Interscience Publishers New York 1967, Vol. 5. 

Nature of soil organic phosphorus an assessment of peak assignments in the diester region of P-31 NMR spectra. Soil Biology and Biochemistry 34, 1467-1477. 

Phosphorus-31 NMR was used by Burton et al, [20] to analyze polyphospha-zenes (dispersants) bound to the surface of alumina ceramic particles. The differences between the spectra of the inorganic polymer in solution and in colloidal suspensions were used to probe the chemical interaction with the alumina. Their P NMR results showed a small lower frequency shift associated with phosphazenes bound to alumina. Solution samples consistently displayed a broadening of the P resonance upon cumulative addition of alumina to the suspension, indicating some degree of chemical adsorption (Sec. II.E). However, Burton et al. pointed out that this lineshape difference might be mistaken as an artifact caused by the amount of solids present in the NMR sample. 

Phosphorus-31 NMR spectroscopy - is very useful in studying phosphine complexes. Normally all the ligand protons are decoupled so as to simplify the spectra. The only common exception is the determination of n in H M(PR3) . This can be done by decoupling only the PR3 protons, while leaving the hydride protons undecoupled.The phosphorus resonance will then appear as an n -I- 1 multiplet. MoH6(PR3)3 could be identified only in this way, because it could only be obtained in an impure form. ... 

The series of molecules which has guided us through this book so far was chosen for a good reason it allowed us to discuss in detail the most important nuclei, the proton and carbon-13, while demonstrating the effect of a very important heteronucleus , phosphorus-31, on the spectra of the two key nuclei. In addition, we could discuss the NMR investigation of this heteronucleus, which exists in 100% natural abundance and has a spin of Vi> and in contrast of oxygen-17, a low-abundance nucleus with a spin greater than Vi. 

An important result of the multinuclear NMR investigations of 23— 25, 27, 28, and 31-35 is that the structures, in contrast to aggregates of monometalated secondary phosphanes and arsanes, are retained in solution. Thus, the phosphandiide derivatives here discussed show resonance signals in their 31P NMR spectra that are independent of concentration and temperature (see Table III). The 31P and 27A1 NMR chemical shifts of 23-25, 27, and 31-35 differ with respect to ring size of the clusters and electronic influences by the substituents at phosphorus and aluminum. 

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