Crystallographic Snapshots of Pre- and Post-Lanthanide Halide Hydrolysis─Reaction Products Captured by the 4-Amino-1,2,4-triazole Ligand

Reactions of lanthanide-(III) chloride salts with 4-amino-1,2,4-triazole (4-NH2-1,2,4-Triaz) in azole melts have led to the isolation of both hydrolysis and nonhydrolysis products in the same synthesis, with the inclusion of a variety of ligands, anions, and water, allowing us to capture crystallographic snapshots of different forms and intermediate hydrolysis fragments. The structural studies reported here include anhydrous and hydrated nonhydrolyzed complexes, which were isolated alongside hydrolysis products, giving oxide/hydroxide lanthanide-(III) dimers, tetramers, and ultimately hexamers. The compounds isolated include [Nd2Cl6(μ2-4-NH2-1,2,4-Triaz)4(4-NH2-1,2,4-Triaz)2], [Ce2Cl4(μ2-Cl)2(μ2-4-NH2-1,2,4-Triaz)4]n, [Ce2(μ2-Cl)4(μ2-OH)2(μ2-4-NH2-1,2,4-Triaz)2]n, [Ln4Cl4(μ2-Cl)4(μ3-OH)4(μ2-4-NH2-1,2,4-Triaz)4]n·2nH2O (Ln = Ce, Nd), and [Ce6Cl6(μ6-O0.5)-(μ3-Cl0.5)4(μ3-Cl0.75)3(μ3-OH)0.75(μ2-4-NH2-1,2,4-Triaz)12((OH2)0.25)2]2[CeCl6]-[Cl9]·xH2O. In all complexes, all lanthanide atoms are pairwise connected via one or more 4-NH2-1,2,4-Triaz ligands and sometimes additional Cl- anions.