High-yield synthesis of heavy rare earth(iii) anhydrous solvates: known, new, and unexpected products

Ten anhydrous rare-earth (RE) chloride solvates were prepared by dehydration of RECl3·6H2O with triethylorthoformate (teof) in O-donor solvents as an accessible and general synthetic route. Reactions are quick, safe, mild, easily reproducible, and cost-effective. They run at room temperature or under reflux to give high-yield, pure crystalline products that are either new, such as [Gd2Cl4(μ-Cl)2(PriOH)6] (1) and [{GdCl(μ-Cl)2(thf)2}∞] (2), or obtained for the first time from teof, such as [GdCl3(thf)4] (3), trans-[MCl2(thf)5]trans-[MCl4(thf)2], M = Gd (4), Dy (6), and Y (7), [YbCl3(thf)3] (8), and [MCl3(dme)2], M = Gd (5), Dy (9), and Er (10). Structural and spectroscopic characterization is presented for all products, and variable-temperature magnetic susceptibility data are discussed for the Dy3+ complexes 6 and 9. The latter behaves as a field-induced single-ion magnet for which theoretical (ab initio) and experimental data allowed a non-trivial assignment of overlapping high- (Orbach, Ueff 139 cm−1) and low-temperature (Raman, weff 46.8(2) cm−1) magnetic relaxation mechanisms (1 kOe field). Besides the main products, unanticipated Lewis and redox reactivity led to serendipitous 11, [({Gd3Cl4(μ-Cl)4(μ-H3CCOO)(C3H8O2)(PriOH)4}·PriOH)∞], and 12, [{(thf)2Cl2Gd(μ-Cl)2(μ3-O2)Gd(thf)3}2]·3thf, whose formation is discussed. The final RE3+ anhydrous complexes serve as valuable starting materials for numerous substitution reactions in coordination and organometallic chemistry.