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

Using 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 center dot 7H(2)O, [C(2)mim](3)[CeCl6] ([C(2)mim](+) = 1-ethyl-2-methylimidazolium), and Ce(NO3)(3)center dot 6H(2)O. Although unsuccessful in our goal, structural analysis revealed that neutral 4-NH2-1,2,4-Triaz is structure directing via eta(2)mu(2)kappa(2) bridging, with the formation of the dinuclear complexes [Ce2Cl2(mu(2)-4-NH2-1,2,4-Triaz)(4)(H2O)(8)]Cl-4 center dot 4H(2)O, [Ce-2(mu(2)-4-NH2-1,2,4-Triaz)(4)(4-NH2-1,2,4-Triaz)(2)(Cl)(6)], and [4-NH2-1,2,4-HTriaz][Ce-2(mu(2)-4-NH2-1,2,4-Triaz)(2)(mu(2)-NO3)(NO3)(6)(H2O)(2)]. When the synthetic conditions favored hydrolysis, the hexanuclear Ce(III) complex [Ce-6(mu(3)-O)(4)(mu(3)-OH)(2)(mu(3)-Cl)(2)(Cl)(6)(mu(2)-4-NH2-1,2,4-Triaz)(12)]center dot 7H(2)O 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.