Facile Construction of Yttrium Pentasulfides from Yttrium Alkyl Precursors: Synthesis, Mechanism, and Reactivity

Treatment of the yttrium dialkyl complex TpMe2Y­(CH2Ph)2­(THF) (TpMe2 = tri­(3,5 dimethylpyrazolyl)­borate, THF = tetrahydrofuran) with S8 in a 1:1 molar ratio in THF at room temperature afforded a yttrium pentasulfide TpMe2Y­(κ4-S5) (THF) (1) in 93% yield. The yttrium monoalkyl complex TpMe2CpYCH2Ph­(THF) reacted with S8 in a 1:0.5 molar ratio under the same conditions to give another yttrium pentasulfide [(TpMe2)2Y]+­[Cp2Y­(κ4-S5)]− (10) in low yield. Further investigations indicated that the S5 2– anion facilely turned into the corresponding thioethers or organic disulfides, and released the redundant S8, when it reacted with some electrophilic reagents. The mechanism for the formation of the S5 2– ligand has been investigated by the controlling of the reaction stoichiometric ratios and the stepwise reactions.