Scandium salt

Scandium salts are colorless, and give gelatinous precipitates with potassium hydroxide and sodium carbonate. The sulfate crystallizes with difficulty. 

The spectra of scandium and ytterbium were first studied by Tobias Robert Thalen (22, 32). Although scandium salts possess no visible... 

A number of compounds of scandium salts with cyclic crown polyethers have been described.80 They comprise Sc(NCS)3(b-15-c-5)-1.5(THF)-2H20, Sc(NCS)3(db-18-c-... 

Like the hydroxides of the Rare earth, scandium hydroxide, Sc(OH)3, is precipitated by addition of alkalies to solutions of scandium salts however, the latter is precipitated at pH 4.9, while the former require pH 6.3 or more, a property which is utilized in one method of separation. Upon heating the hydroxide (or certain oxyatid salts), scandium oxide. Sc>C>3 is produced. Scandium hydroxide is less acidic than aluminum hydroxide, requiring boiling KOH solution to form the complex potassium compound, K2[Sc(OH)5 H 0] 3H 0. 

Another variation on this theme is the use of a scandium salt of a hydrophobic polystyrene-supported sulfonic acid (PS-S03H) as an effective heterogeneous Lewis acid catalyst in aqueous media [149]. 

Although other scandium salts have recently been reported in the literature, their properties are similar to Sc(OTf)3 in many respects, and so this article surveys useful synthetic reactions which employ Sc(OTf)3 as a catalyst, focusing in particular on carbon-carbon bond-forming reactions in organic solvents, aqueous media, and the solid phase. 

Although Sc(OTf)3 and other scandium salts are water-stable and used in aqueous media, they are also successfully employed in organic media. They are used catalyti-cally in many reactions and can often be recovered and reused because they are stable under usual water-quenching conditions. 

Other scandium perfluoroalkanesulfonates such as the pentafluoroethanesulfonate and nona-fluorobutanesulfonate have also been shown to be good catalysts.204 Scandium salts such as the perchlorate and alkylsulfates205 are also active catalysts. 

In addition to lanthanides, yttrium and scandium salts, which appear in the same column of Mendelejew periodic table, were also shown to act as Lewis acid... 

Morin, the coloring matter of fustic, is 3,5,7,2, 4 -pentahydroxy flavone (I). Its alcohol solutions react with aluminum salts in neutral or acetic acid solution to give an intense green fluorescence in daylight and ultraviolet light. The fluorescence is due to the formation of a colloidally dispersed inner complex aluminum salt of morin with the probable structure (II), or to an adsorption compound of morin with alumina. Beryllium, indium, gallium, thorium and scandium salts also form fluorescent compounds with morin. The pH of the system has much influence in these reactions. The only metal ion whose reaction with morin is independent of pH is Zr+ or its hydrolysis product (compare page 519). 

Diels-Alder reactions are one of the most important classes of cycloaddition reactions. They are, however, commonly associated with moisture-sensitive Lewis acids, such as AICI4, TiCU, and SnCU. Scandium salts are known as powerful catalysts for many types of Diels-Alder reactions [23, 24]. Recent advances have been focused on immobilization of Sc catalysts to explore new reactions. 

Recently, Sc(OTf)3 has been widely used in many protection reactions such as methoxymethylation [69], tetrahydropyranylation [70], O-glycosidation [71], acylation [72, 73], esterification of alcohols [74], and thioglycosidation of glycols [75]. Scandium salts such as Sc(OTf)3 and SCCI3 were also found to be efficient and recyclable catalysts for conversion of carbonyl compounds to 1,3-oxathiolanes, 1,3-dithiolanes, and 1,3-dithianes [76, 77]. By employing this protocol, chemose-lective oxathioactalization of aldehydes in the presence of ketones was achieved (Scheme 12.34) [78]. 

It was reported that Aza-Diels-Alder reaction of Danishefsky s diene (26) with imines 28 smoothly proceeded in supercritical CO2 under catalysis by lithium heptadecafluorooctanesulfonate (Scheme 17) [34], A nonpolar long per-fluorinated alkyl chain of the catalyst allowed its solubility in supercritical CO2 and therefore ensured effective homogenous catalysis. Scandium salt of die same acid also demonstrated great catalytic properties in this reaction [35]. 

The concentration, counterion and pH dependences of 6( Sc) in aqueous solutions of scandium salts have revealed equilibria between outer-sphere versus inner-sphere complexes (contact ion pairs versus direct coordination of the anion), in addition to the equilibria between [Sc(H20)g], which is present at low pH, its deprotonation ([Sc(H20)5(0H)]2+) and oligomerization products ([Sc2(H20),(0H)2l N (Sc3(H20) (0H)4l +). present at pH values up to 4, and [Sc(OH)4]", the species that is formed at high pH. 

Scandium salts in excess N2H4-H20 + CO2 Li2C03 + aqueous N2HgBeF4 Cu(N2H3COO)2 + 85% HF... 

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