PHIP-NMR-Spectroscopy

Complexes of the type (l I)(C1) Rh(PMet)2(//-Cl)(y -l I) Rh(CO)(PMet) and [(H)(Cl)Rh(PMe3)2(yM-I)(jM-H)Rh(CO)(PMe3)], with NMR data corresponding to our results, have also been observed before by Duckett, Eisenberg, and coworkers, using PHIP-NMR spectroscopy [30, 31]. 

Table 12.5 Reactions studied using 13C-PHIP-NMR spectroscopy.

Although this phenomenon provides a powerful tool for the NMR investigation of low-y nuclei, the full potential of this sizeable polarization transfer from parahydrogen to other nuclei has not been applied very much as compared to H-PHIP-NMR spectroscopy. In particular, the use of the PHIP effect to en-... 

Comment Whether it is used for simple monitoring, or to prove the existence of traces of a key intermediate (EXSY or PHIP), NMR spectroscopy has clearly developed into one of the catalytic community s most valuable analytical tools. NOE data will never afford a molecular picture which is quite as structurally exact as that from X-ray crystallography however, this latter method cannot determine kinetic parameters, recognize equilibria, mimic catalytic conditions (HP) or recognize when ion-pairing is important (PGSE). NMR is not a very sensitive method indeed, most methods are far more amenable to quantitative results. Nevertheless, its proven flexibility makes it indispensable. 

Figure 9.17 The first rhodium dihydrides in enantioselective enamide hydrogenation that were detected using PHIP NMR spectroscopy. A Experimental spectrum. B Computer simulation [36].

Hubler P, Giemoth R, Kununerle G, Bargon J (1999) Investigating the kinetics of homogeneous hydrogenation reactions using PHIP NMR spectroscopy. J Am Chem Soc 121 5311-5318... 

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