f-Element Zintl Chemistry: Actinide-Mediated Dehydrocoupling of H₂Sb^1– Affords the Trithorium and Triuranium Undeca-Antimontriide Zintl Clusters [{An(Tren^TIPS)}₃(μ₃-Sb₁₁)] (An = Th, U; Tren^TIPS = {N(CH₂CH₂NSiⁱPr₃)₃}^3–)

Abstract

Reaction of the cesium antimonide complex [Cs(18C6) 2 ][SbH 2 ] (1, 18C6 = 18-crown-6 ether) with the triamidoamine actinide separated ion pairs [An(Tren TIPS )(L)]-[BPh 4 ] (Tren TIPS = {N(CH 2 CH 2 NSi i Pr 3 ) 3 } 3− ; An/L = Th/DME (2Th); U/THF (2U)) affords the triactinide undeca-antimontriide Zintl clusters [{An(Tren TIPS )} 3 (μ 3 -Sb 11 )] (An = Th (3Th), U (3U)) by dehydrocoupling. Clusters 3Th and 3U provide two new examples of the Sb 11 3− Zintl trianion and are unprecedented examples of molecular Sb 113− being coordinated to anything since all previous reports featured isolated Sb 11 3− Zintl trianions in separated ion quadruple formulations with noncoordinating cations. Quantum chemical calculations describe dominant ionic An−Sb interactions in 3Th and 3U, though the data suggest that the latter exhibits slightly more covalent An−Sb linkages than the former. Complexes 3Th and 3U have been characterized by single crystal X-ray diffraction, NMR, IR, and UV/vis/NIR spectroscopies, elemental analysis, and quantum chemical calculations.