Could anyone please explain how and when 195Pt satellites can disappear from 13C NMR spectra in 2JPt-P-C or 3JPt-P-C-C heterocoupled systems? Thanks.
Imre, one reason they can disappear is when 195 Pt relaxation becomes too fast due to CSA. 195 Pt satellites can be present in spectra at lower field, broaden at intermediate fields and disappear at high fields.
Clemens
Imre, I agree with Clemens, one possible contribution can be added, namely the dipolar one between the attached 13C and the 195 Pt, to some extent this also can broaden the satelittes. This is not field dependent.
Of course one must not forget about the possibilty of a fast exchange!
Gábor
For 3J Karplus equation (dihedral angle) can also help explain the decrease in coupling constant.
Sander, indeed 3J angles and even 4J (W-coupling) angles can influence the magnitude and sign of couplings. However, this case all the 2J and 3J (and 4J?) platinum satellites disappear (broaden away) due to the fact that the relaxation of 195Pt becomes too fast for detection above a certain magnetic field strength (which originates from the principle of chemical shift anisotropy). Thus, the xJPt-C coupling constants do not decrease or change.
A nice example (with 199Hg instead of 195Pt) is given by R. Benn, H. Guenther et al. in Angew. Chem. Int. Ed. Engl. 1982, 21, 295-296. Describes the behaviour of the satellites in 1H and 13C spectra as a function of B0 with figures.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders