Nmr Diffusion Methods In Inorganic And Organometallic Chemistry

The basic approach associated with PGSE and DOSY NMR diffusion methods is described. These methods can be applied in coordination and organometallic chemistry in order to a) estimate molecular and ionic volumes (and thereby obtain support for the formation of clusters, oligomers, dendrimers and other aggregates and b) recognize hydrogen bonding and ion pairing via an analysis of the separately measured diffusion constants (D-values) from, for example, the two ions of a salt. With respect to ion pairing, this often involves the use of H-1 data to obtain the D-value of an organometallic cation and then F-19 measurements from a fluorine containing anion such as BF4-, PF6-, OTf-, BArF- or B(C6F5)(4)(-). The estimates of the extent of ion pairing can be carried out in both polar and non-polar solvents and the molecular volumes obtained correlate well with estimates from x-ray crystallography.