Scandium complexes bromides

Scandium complexes readily with 8-hydroxyquinolinate ion. Many years ago, Sc(hq)3-Hhq, which was obtained from aqueous solution, was described,97 and this compound does not lose Hhq cleanly on heating but does so in benzene solution.98 However, it has been stated that the solid deposited at about pH 7 is in fact Sc(hq)3." More recently, stability constant values have been determined for the Sc3+/hq-/50% aqueous dioxane system and the corresponding 2-methyl-8-hydroxyquinoline system.100 Chinese workers, who are showing some interest in spectrophotometric analysis, have detected Sc3+ on the microgram scale by fluorometry using -5-sulfonate and cetyltrimethylammonium bromide as an extractant... 

FIGURE 44 The structure of [(LMgBr)2ScBr] (L = pentane-2,4-di(2-diethylaminoethyl) diketiminate), prepared by the reaction of [LScBr2] with two equivalents of allylmagnesium bromide. Theoretical studies are consistent with the monovalent nature of scandium in this complex. Figure was redrawn after Neculai et al. (2002). 

The fact that the scandium(III) ion has the 3d electronic configuration severely limits the kinds of physical methods that can be brought to bear on determining the nature of the chemical environment in its complexes. The Sc nuclide has 100% natural abundance and a high sensitivity compared to protons and NMR studies using Sc may well prove to be a powerful tool (Melson et al., 1974). NMR spectra of aqueous solutions of scandium(III) chloride, perchlorate, nitrate, and sulfate have been obtained and it has been demonstrated that the chemical shifts for Sc at very low concentrations for the chloride, bromide, and perchlorate are independent of the anion and may be characteristic of the [Sc(OH)] ion. At higher concentrations the chemical shifts are both anion- and concentration-dependent and reflect the formation of bromo and chloro complexes and in the case of the perchlorate, polymeric hydroxo species. The chemical shifts for the nitrate and sulfate are different from the others and indicate that even at low concentrations there must be significant quantities of the respective complexes. 

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