Dehydration of scandium chloride hydrate: synthesis and molecular structures of ScCl 3(η 2-DME)(MeCN), ScCl 3(diglyme) and [Sc 2(μ-OH) 2(H 2O) 10]Cl 4·2H 2O

Abstract

Various dehydration procedures have been evaluated for ScCl 3·6H 2O. The ScCl 3(DME)(MeCN) 1 and ScCl 3(diglyme) 2 [diglyme=MeO(CH 2CH 2O) 2Me] adducts have been synthesized by a ligand-exchange reaction from ScCl 3(THF) 3 in acetonitrile. The diglyme adduct could also be obtained by dehydration of ScCl 3·6H 2O by trimethylchlorosilane in diethylether in the presence of the ligand. The complexes were characterized by FT–IR, 1H NMR and by X-ray diffraction. They both correspond to monomeric species based on distorted hexacoordinated scandium. Hydrolysis of 2 gave [Sc 2(μ-OH) 2(H 2O) 10]Cl 4·2H 2O, 3. The Sc–O coordination bonds of 1 and of 2 [2.207(1) Å for the DME adduct, 2.165(8)–2.257(9) Å for 2] have lengths comparable to the Sc–O(H 2O) bonds of 3 [2.172(4)–2.217(5) Å], but were longer than the Sc–OH ones [2.064(5) Å]. The dimeric cations, in which the metals are heptacoordinated, are associated by hydrogen bonding (∼ 2.737(5) Å) between coordinated and crystallization-type water molecules. As a result, chains are developed along the a axis.