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

Treatment of the yttrium dialkyl complex TpMe2 Y(CH2 Ph)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 TpMe2 Y(κ4 -S5 ) (THF) (1) in 93% yield. The yttrium monoalkyl complex TpMe2 CpYCH2 Ph(THF) reacted with S8 in a 1:0.5 molar ratio under the same conditions to give another yttrium pentasulfide [(TpMe2 )2 Y]+ [Cp2 Y(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.