59Cobalt (59Co) is a high sensitivity nucleus with a 100% natural abundance that yields somewhat broad lines even in symmetric environments and very broad lines for slightly larger complexes over an extremely wide chemical shift range. 59Co is a spin 7/2 nucleus and is therefore quadrupolar. As a result, the signal width increases with asymmetry of the environment. The most common oxidation state of cobalt salts is Co(II). However, this is paramagnetic so cannot be observed on a high resolution NMR spectrometer. 59Co NMR is observable for Co(III), Co(I) and some clusters that are formally Co(0) or Co(-I). 59Co NMR is used for studying small Co complexes. Each type of cobalt compound has its characteristic chemical shift (fig. 1).
Fig. 1. Chemical shift ranges for cobalt NMR
We do not have experience of 59Co NMR in our laboratory but could provide the service if given an appropriate sample.
|Chemical shift range||18000 ppm, from -4000 to 14000|
|Frequency ratio (Ξ)||23.727074%|
|Reference compound||0.56 m K3[Co(CN)6] in D2O|
|Linewidth of reference||5 Hz|
|T1 of reference||0.1 s|
|Receptivity rel. to 1H at natural abundance||0.278|
|Receptivity rel. to 1H when enriched||0.278|
|Receptivity rel. to 13C at natural abundance||1640|
|Receptivity rel. to 13C when enriched||1640|
|Linewidth parameter||240 fm4|
Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, cobalt salts are toxic.