Lanthanides synthesis, sodium salts

The sodium salt may be obtained by adding a dilute NaOH solution to attain pH 5.0. One of the main precautions is that the synthesis be done with dilute solutions. For example nitrilotriacetic acid (NTA) complexes have been synthesized using 0.02 M solutions and at higher dilutions in the case of heavy lanthanides [37]. Use of an excess of lanthanide oxide should be avoided since reactions of the following type may take place [38]... 

The synthesis of the first half-metallocene bis(borohydrides) of lanthanide elements has been achieved by a reaction of the tetraisopropylcyclopentadienyl sodium salt NafCsHPr ) with Ln(BH4)3(THF)3 (Ln = Sm, Nd) at room temperature to afford the monocyclopentadienyl complexes (CsHPr 4)Sm(BH4)2(THF) and (CsHPr 4)Nd(BH4)2(THF) in 50-60% yield. These complexes are thermally stable and melt without decomposition at around 170 °C.307 Analogous compounds have also been synthesized with the use of the [CsMe4Prn] ligand.308... 

The lanthanide triflate remains in the aqueous phase and can be re-used after concentration. From a green chemistry viewpoint it would be more attractive to perform the reactions in water as the only solvent. This was achieved by adding the surfactant sodium dodecyl sulfate (SDS 20 mol%) to the aqueous solution of e.g. Sc(OTf)3 (10 mol%) [145]. A further extension of this concept resulted in the development of lanthanide salts of dodecyl sulfate, so-called Lewis acid-surfactant combined catalysts (LASC) which combine the Lewis acidity of the cation with the surfactant properties of the anion [148]. These LASCs, e.g. Sc(DS)3, exhibited much higher activities in water than in organic solvents. They were shown to catalyze a variety of reactions, such as Michael additions and a three component a-aminophosphonate synthesis (see Fig. 2.44) in water [145]. 

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