Late to the Party: Synthesis and Characterization of Tellurium and Selenium Half-Sandwich Complexes

We report the synthesis and characterization of the first series of tellurium and selenium complexes featuring an η5-cyclopentadienyl ligand. Reaction of Ph3TeX (X = Cl, S2CNEt2) with MCpR (M = Li, K; R = H, Me4, Me5) results in high yields of [Cp]­[TePh3] (1), [CpMe4]­[TePh3] (2), and [Cp*]­[TePh3] (3), respectively. Similarly, reaction of Ph3SeCl with LiCp and KCp* furnishes [Cp]­[SePh3] (4) and [Cp*]­[SePh3] (5). Each was characterized by X-ray crystallography, revealing similar η5-coordination with little distortion from an idealized half-sandwich geometry, presumably from the remaining lone pair on tellurium and selenium. The Te–centroid distances are relatively long (1: 2.770(3), 2: 2.746(1), and 3: 2.733(1) Å), suggesting a mostly ionic interaction. Se–centroid distances (4: 2.748(3), 5: 2.707(2), 2.730(2) Å) were found to be surprisingly similar despite its smaller atomic radius. Compounds 2, 3, and 5 display rapid decomposition at room temperature, extruding a phenylated cyclopentadiene and the respective diphenylchalcogenide. The nature of bonding within these complexes was investigated through DFT methods and found to be primarily ionic in nature.本工作报道了首例含η⁵-环戊二烯基配体(η⁵-cyclopentadienyl ligand)的碲与硒配合物系列的合成与表征。三苯基碲衍生物(Ph₃TeX，X=氯、二乙基二硫代氨基甲酰基)与金属环戊二烯基(Cyclopentadienyl, 缩写Cp)试剂(MCpR，M=锂、钾；R=氢、四甲基、五甲基)反应，可分别以优异收率得到配合物1([Cp][TePh₃])、2([四甲基环戊二烯基(tetramethylcyclopentadienyl, 缩写CpMe4)][TePh₃])与3([五甲基环戊二烯基(pentamethylcyclopentadienyl, 缩写Cp*)][TePh₃])。类似地，三苯基硒氯化物(Ph₃SeCl)分别与环戊二烯基锂(LiCp)和五甲基环戊二烯基钾(KCp*)反应，得到配合物4([Cp][SePh₃])与5([Cp*][SePh₃])。通过X射线晶体衍射表征(X-ray crystallography)对所有配合物进行了分析，结果显示所有配合物均具有相似的η⁵-配位模式，与理想化的半三明治几何构型偏差极小，该现象推测源于碲与硒原子上剩余的孤对电子。碲-环戊二烯基质心距离相对较长（配合物1：2.770(3)、配合物2：2.746(1)、配合物3：2.733(1) Å），表明其相互作用主要为离子型。硒-环戊二烯基质心距离（配合物4：2.748(3)、配合物5：2.707(2)、2.730(2) Å）虽硒原子半径更小，但测得的距离却出人意料地相近。配合物2、3与5在室温下可快速分解，释放出苯基取代环戊二烯与相应的二苯基硫族化物。通过密度泛函理论(Density Functional Theory, DFT)方法对上述配合物的成键本质进行了研究，结果表明其成键作用主要为离子型。