Molecular Thorium Compounds with Dichalcogenide Ligands: Synthesis, Structure, 77Se NMR Study, and Thermolysis

A series of dimeric thorium disulfides and diselenides have been prepared with sterically undemanding ancillary ligands. Five complexes, (py)6Th2I4(μ2-S2)2, (py)6Th2Br2(SC6F5)2(μ2-S2)2, (py)6Th2I4(μ2-Se2)2, (py)6Th2I2(SC6F5)2(μ2-Se2)2, and (py)6Th2Br2(SC6F5)2(μ2-Se2)2, were isolated in high yields by first reducing mixtures of I2, F5C6SSC6F5, PhSeSePh, or PhSSPh, and PhSeBr with elemental Th, followed by in situ ligand-based redox reactions with elemental sulfur or selenium. These are the first examples of thorium compounds with bridging dichalcogenide ligands. Attempts to prepare chloride derivatives gave mixtures of (py)4ThCl4 and either (py)6Th2Cl2(SC6F5)2(μ2-S2)2 or (py)8Th4Se4(SePh)4(SC6F5)4. All products were characterized by single-crystal and powder X-ray diffraction and IR, UV–visible, and NMR spectroscopy. A computational analysis of experimental 77Se NMR chemical shifts reveals that the solvated dimeric structures with two bridging dichalcogenides are maintained in solution. Thermolysis of (py)6Th2I4(μ2-Se2)2 leads to reduction of the bridging Se22– moieties, oxidation of the I– ligand, and formation of solid-state ThSe2 and I2.本研究以空间位阻需求较低的吡啶(pyridine, py)作为辅助配体，合成了一系列二聚型二硫化钍与二硒化钍配合物。我们通过如下步骤高产率分离得到五种配合物，分别为(py)₆Th₂I₄(μ₂-S₂)₂、(py)₆Th₂Br₂(SC₆F₅)₂(μ₂-S₂)₂、(py)₆Th₂I₄(μ₂-Se₂)₂、(py)₆Th₂I₂(SC₆F₅)₂(μ₂-Se₂)₂与(py)₆Th₂Br₂(SC₆F₅)₂(μ₂-Se₂)₂：首先以金属钍还原碘(I₂)、五氟苯基二硫醚(bis(pentafluorophenyl) disulfide, F₅C₆SSC₆F₅)、二苯二硒(diphenyl diselenide, PhSeSePh)、二苯二硫(diphenyl disulfide, PhSSPh)或苯硒基溴(phenyl selenyl bromide, PhSeBr)的混合体系，随后通过原位配体氧化还原反应，结合单质硫或硒完成目标产物的制备。该系列配合物为首例含桥联二硫属配体的钍基化合物。 尝试合成氯化物衍生物时，得到了(py)₄ThCl₄与(py)₆Th₂Cl₂(SC₆F₅)₂(μ₂-S₂)₂或(py)₈Th₄Se₄(SePh)₄(SC₆F₅)₄的混合产物。所有产物均通过单晶与粉末X射线衍射、红外(infrared, IR)、紫外-可见(ultraviolet-visible, UV-visible)光谱以及核磁共振(nuclear magnetic resonance, NMR)波谱进行了表征。对实验测得的硒-77(⁷⁷Se)核磁共振化学位移开展计算分析后发现，该类配合物在溶液中仍保持带有两个桥联二硫属配体的溶剂化二聚体结构。 对(py)₆Th₂I₄(μ₂-Se₂)₂进行热解时，桥联的Se₂²⁻基团被还原、碘离子(I⁻)配体被氧化，最终生成固态二硒化钍(ThSe₂)与单质碘(I₂)。