Oxygen-17 NMR

Isab, A.A., Shaw, C.E. Ill and Locke, J. (1988) GC-MS and oxygen-17 NMR tracer studies of triethylphosphine oxide formation from auranofin and water- O in the presence of bovine serum albumin an in vitro model for auranofin metabolism. Inorganic Chemistry, 27, 3406-3409. 

Oxygen-17 NMR spectroscopy has an immense potential for structural analysis of cyclic sulfoxides and sulfones as well as for providing insight into the nature of bonding within these two functional groups . Indeed, in addition to data concerning the NMR chemical shifts for several cyclic sulfoxides and sulfones, NMR chemical shift differences between several diastereotopic sulfonyl oxygens in both cyclic and acyclic systems have been reported . 

We shall use our model compound 7 to show how oxygen-17 NMR can be used. Figure 31 shows the spectrum, recorded using a 40% solution of 7 in CD3CN at a temperature of 55°C. 

Bell et al. (2002) investigated the relationship between water mobility as measured by oxygen-17 NMR (transverse relaxation rate obtained from linewidth at half-height) and chemical stability in glassy and rubbery polyvinylpyrrolidone (PVP) systems. Reported results suggest that water mobility in PVP model systems was not related to Tg. The study did not find a link between water mobility and reaction kinetics data (half-lives) for degradation of aspartame, loss of thiamin and glycine, and stability of invertase. 

The substitution and protonation behavior of the rcms-dioxotetra-cyanometalate complexes of Re(V), Tc(V), W(IV), Mo(IV), and Os(VI) have been extensively investigated in the past decade and selected aspects have been reviewed (1, 2). Previous studies demonstrated the use of oxygen-17 NMR in different metal systems (3), including the complex oligomeric Mo(IV) aqueous systems (4), and therefore, since these oxocyano complexes contain an even wider range of nuclei such as 13C, 15N, 170, "Tc, and 183W, they are attractive model complexes to study by multinuclear NMR. Thus, detailed studies on the dynamics therein have been investigated in the past few years (5-8). 

In Table III is also given the distortion of the W(IV) complexes as demonstrated by the displacement from the plane as well as the change in bite angle of the equatorial cyano ligand with the M=0 moiety as well as the v(W = 0) as obtained from IR studies and the oxygen-17 NMR data. It is clear that a reasonable correlation between all these parameters, excluding the chemical shift for the [WO(CN)5]3 complex (Fig. 4a), exists. 

Fig. 8. Oxygen-17 NMR spectra at pH = 1.3, illustrating the formation of the di-nuclear complex at 25°C after (a) 3 min, (b) 1 h and (c) 6 h of mixing [Re02(CN)4]3 and H2170. The total complex concentration [Re] = 0.2 m, /m = 1.0 m (KN03), NMR chemical shift reference is the nitrate ion (<5(N03) = 413 ppm) (5). (Adapted with permission from Roodt, A. Leipoldt, J. G. Helm, L. Merbach, A. E. Inorg. Chem. 1992, 31, 2864-2868. Copyright 1992 American Chemical Society).

In conclusion, oxygen-17 NMR line-broadening provides the unique opportunity to study very fast proton transfer reactions on these metal oxocyano complexes by lowering the concentration of the reacting species through pH manipulation. 

Water exchange rate constants measured by oxygen-17 NMR... 

Oxygen-17 NMR has seldom been used for compounds of this type and all the existing NM( oxazines are collected in Table 7. ... 

Zawodzinski, T. A., Jr. and Osteryoung, R. A., Aspects of the chemistry of water in ambient-temperature chloroaluminate ionic liquids Oxygen-17 NMR studies., Inorg. Chem., 26,2920,1987. 

Table 8 Oxygen-17 NMR shift values of some oxiranes...

D. A. Boykin and A. L. Baumstark in Applications of Oxygen-17 NMR Spectroscopy to Structural Problems in Rigid Planar Organic Molecules , 170 NMR Spectroscop. Org. Chem., CRC Press, New York, 1991, p.154. 

All facets of study have been greatly aided by the ease with which crystal structures may be obtained and by the availability of sensitive Fourier transform NMR spectrometers which allow nuclei such as l70, 51V, wNb, s5Mo, and, K3W to be used for structural studies. Oxygen-17 NMR spectroscopy has proved to be particularly useful because 170 chemical shifts are very sensitive to environment. As a result it is possible to distinguish between terminal and various kinds of bridging oxygen sites. The l70 spectrum of [W Oi, ]2 and its structure are shown in Fig. Ifi-IOa/1 We see... 

III, and IV. Oxygen-17 NMR line-broadening experiments are the technique erf choice for determining rate constants of water exchange of paramagnetic ions when the values of k lie between I03 and I09 s-1. The process that is studied is... 

Janes, N., and E. Oldfield (1986). Oxygen-17 NMR study of bonding in silicates The /-orbital controversy. J. Amer. Chem. Soc. 108, 5743-53. 

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