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

Treatment of the yttrium dialkyl complex Tp^Me2Y­(CH₂Ph)₂­(THF) (Tp^Me2 = tri­(3,5 dimethylpyrazolyl)­borate, THF = tetrahydrofuran) with S₈ in a 1:1 molar ratio in THF at room temperature afforded a yttrium pentasulfide Tp^Me2Y­(κ₄-S₅) (THF) (<b>1</b>) in 93% yield. The yttrium monoalkyl complex Tp^Me2CpYCH₂Ph­(THF) reacted with S₈ in a 1:0.5 molar ratio under the same conditions to give another yttrium pentasulfide [(Tp^Me2)₂Y]⁺­[Cp₂Y­(κ₄-S₅)]⁻ (<b>10</b>) 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

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

Treatment of the yttrium dialkyl complex Tp^Me2Y­(CH₂Ph)₂­(THF) (Tp^Me2 = tri­(3,5 dimethylpyrazolyl)­borate, THF = tetrahydrofuran) with S₈ in a 1:1 molar ratio in THF at room temperature afforded a yttrium pentasulfide Tp^Me2Y­(κ₄-S₅) (THF) (<b>1</b>) in 93% yield. The yttrium monoalkyl complex Tp^Me2CpYCH₂Ph­(THF) reacted with S₈ in a 1:0.5 molar ratio under the same conditions to give another yttrium pentasulfide [(Tp^Me2)₂Y]⁺­[Cp₂Y­(κ₄-S₅)]⁻ (<b>10</b>) 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

Rare-Earth-Metal-Catalyzed Addition of Terminal Monoalkynes and Dialkynes with Aryl-Substituted Symmetrical or Unsymmetrical Carbodiimides

A high-efficiency and atom-economic route for the synthesis of N-aryl-substituted propiolamidines was established through the addition of terminal alkynes with aryl-substituted symmetrical or unsymmetrical carbodiimides catalyzed by mixed Tp^Me2/Cp rare-earth-metal alkyl complexes (Tp^Me2)­CpLnCH₂Ph­(THF) (<b>1</b>^<b>Ln</b>). Moreover, the gadolinium alkyl complex <b>1</b>^<b>Gd</b> can also serve as a catalyst for the double addition of dialkynes with carbodiimides. Mechanism studies indicated that the variable coordination modes (κ³ or κ²) of the Tp^Me2 ligand on the rare-earth-metal species may play an important role in the catalytic cycles

Versatile Reactivity of β‑Diketiminato-Supported Yttrium Dialkyl Complex toward Aromatic N‑Heterocycles

The reactions of β-diketiminatoyttrium dialkyl complex LY­(CH₂Ph)₂(THF) (<b>1</b>, L = [{N­(2,6-^<i>i</i>Pr₂C₆H₃)­C­(Me)}₂CH]⁻) with a series of aromatic N-heterocycles such as 2-phenylpyridine, benzothiazole, and benzoxazole were studied and displayed discrete reactivity including C–H activation, C–C coupling, ring-opening/insertion, and dearomatization. The reaction of <b>1</b> with 2-phenylpyridine in 1:2 molar ratio in THF at 30 °C for 14 days afforded a structurally characterized metal complex, LY­(η²-<i>N,C</i>-C₅H₄NC₆H₄-2)­[C₅H₄N­(CH₂Ph-4)­Ph] (<b>2</b>), in 73% isolated yield, indicating the occurrence of phenyl ring C­(sp²)–H activation and pyridine ring 1,4-addition/dearomatization. However, when this reaction was done at 5 °C for 7 days, it gave the pyridine ring 1,2-addition product LY­(η²-<i>N,C</i>-C₅H₄NC₆H₄-2)­[C₅H₄N­(CH₂Ph-2)­Ph] (<b>3</b>) in 54% isolated yield. Further investigations revealed that complex <b>2</b> is the thermodynamic controlled product and complex <b>3</b> is the kinetically controlled product; <b>3</b> converted slowly into <b>2</b>, as confirmed by ¹H NMR spectroscopy. The equimolar reaction of <b>1</b> with benzothiazole or benzoxazole produced two C–C coupling/ring-opening/insertion products, LY­[η²-<i>S,N</i>-SC₆H₄NCH­(CH₂Ph)₂]­(THF) (<b>4</b>) and {LY­[μ-η²:η¹-<i>O,N</i>-OC₆H₄NCH­(CH₂Ph)₂]}₂ (<b>5</b>), in 84% and 78% isolated yields, respectively