Trapping an Unexpected/Unprecedented Hexanuclear Ce(III) Hydrolysis Product with Neutral 4‐Amino‐1,2,4‐triazole

Abstract

AbstractUsing Ce(III) as both a representative lanthanide and actinide analog, the ability of mixtures of acidic and basic azoles to allow direct access to homoleptic N‐donor f‐element complexes in one pot reactions from hydrated salts as starting materials was examined by reacting mixtures of 4‐amino‐1,2,4‐triazole (4‐NH2‐1,2,4‐Triaz), 5‐amino‐tetrazole (5‐NH2‐HTetaz), and 1,2,3‐triazole (1,2,3‐HTriaz) in 1 : 1 and 1 : 3 ratios with CeCl3 ⋅ 7H2O, [C2mim]3[CeCl6] ([C2mim]+=1‐ethyl‐2‐methylimidazolium), and Ce(NO3)3 ⋅ 6H2O. Although unsuccessful in our goal, structural analysis revealed that neutral 4‐NH2‐1,2,4‐Triaz is structure directing via η2μ2κ2 bridging, with the formation of the dinuclear complexes [Ce2Cl2(μ2‐4‐NH2‐1,2,4‐Triaz)4(H2O)8]Cl4 ⋅ 4H2O, [Ce2(μ2‐4‐NH2‐1,2,4‐Triaz)4(4‐NH2‐1,2,4‐Triaz)2(Cl)6], and [4‐NH2‐1,2,4‐HTriaz][Ce2(μ2‐4‐NH2‐1,2,4‐Triaz)2(μ2‐NO3)(NO3)6(H2O)2]. When the synthetic conditions favored hydrolysis, the hexanuclear Ce(III) complex [Ce6(μ3‐O)4(μ3‐OH)2(μ3‐Cl)2(Cl)6(μ2‐4‐NH2‐1,2,4‐Triaz)12] ⋅ 7H2O was isolated. This unexpected hydrolysis product represents the first example of a high nuclearity lanthanide complex where all Ln atoms are pairwise connected through 12 N‐donor ligands or 12 neutral bridging ligands of any type, a rare example of incorporation of non‐oxo coordinating anions in the M6X8 core, and the first reported Ce(III) hexanuclear complex of this type.