Li+, Cu+, and Ag+ Oligonuclear Structures with the Sterically Demanding Bis(3,5-tertbutylpyrazol-1-yl)dithioacetate Heteroscorpionate Ligand

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• 作者：Irene Bassanetti ; Marcello Gennari ; Luciano Marchi ; Mattia Terenghi ; Lisa Elviri
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：August 2, 2010
• 年：2010
• 卷：49
• 期：15
• 页码：7007-7015
• 全文大小：1035K
• 年卷期：v.49,no.15(August 2, 2010)
• ISSN：1520-510X

文摘

The heteroscorpionate N₂S₂ donor ligand bis(3,5-tertbutylpyrazol-1-yl)dithioacetate (L) was prepared as a Li⁺ trinuclear complex, which co-crystallizes with tetrahydrofuran (THF) solvent molecules: [Li(L)]₃·(2.25)THF. When [Li(L)]₃ was reacted with AgBF₄ or [Cu(CH₃CN)₄]BF₄, the oligonuclear species [Ag(L)]₃ and [Cu₅(L)₄]BF₄ were isolated and structurally characterized. The Ag⁺ complex presents an irregular trinuclear structure in which three AgL moieties define a central trigonal site that may potentially host a fourth metal ion. The Cu⁺ complex exhibits a highly symmetric pentanuclear structure in which four equivalent CuL moieties shape an internal tetrahedral site occupied by an additional Cu⁺ ion. According to electrospray-mass spectrometry (ESI-MS) and ¹H diffusion NMR spectroscopy, the Ag⁺ and Cu⁺ complexes maintain oligonuclear structures in solution. In particular, the Cu⁺ pentanuclear complex, once dissolved, rapidly equilibrates with the tetranuclear species [Cu₄(L)₃]⁺. This is confirmed by the presence of two sets of NMR signals, which demonstrated a change in ratio at different complex concentrations effected by a NMR dilution titration. Variable temperature NMR experiments (210−303 K) defined the activation parameters associated with the fluxional behavior of [Cu₅(L)₄]BF₄ and [Cu₄(L)₃]⁺, and these results are consistent with intramolecular rearrangements in both species (ΔS < 0).