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

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