Geminally Substituted Tris(acenaphthyl) and Bis(acenaphthyl) Arsines, Stibines, and Bismuthine: A Structural and Nuclear Magnetic Resonance Investigation

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• 作者：Brian A. Chalmers ; Christina B. E. Meigh ; Phillip S. Nejman ; Michael Bühl ; Tomáš Lébl ; J. Derek Woollins ; Alexandra M. Z. Slawin ; Petr Kilian
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 18, 2016
• 年：2016
• 卷：55
• 期：14
• 页码：7117-7125
• 全文大小：528K
• 年卷期：0
• ISSN：1520-510X

文摘

Tris(acenaphthyl)- and bis(acenaphthyl)-substituted pnictogens (iPr₂P-Ace)₃E (2–4) (E = As, Sb, or Bi; Ace = acenaphthene-5,6-diyl) and (iPr₂P-Ace)₂EPh (5 and 6) (E = As or Sb) were synthesized and fully characterized by multinuclear nuclear magnetic resonance (NMR), high-resolution mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. The molecules adopt propeller-like geometries with the restricted rotational freedom of the sterically encumbered iPr₂P-Ace groups resulting in distinct NMR features. In the tris(acenaphthyl) species (2–4), the phosphorus atoms are isochronous in the ³¹P{¹H} NMR spectra, and the rotation of the three acenaphthyl moieties around the E–C_ipso bond is locked. On the other hand, the bis(acenaphthyl) species show a fluxional behavior, resulting in an AX to A₂ spin system transition in the ³¹P{¹H} variable-temperature NMR spectra. This allowed elucidation of remarkable through-space couplings (^8TSJ_PP) of 11.5 Hz (for 5) and 25.8 Hz (for 6) at low temperatures. In addition, detailed line shape analysis of the thermodynamic parameters of the restricted rotation of the “propeller blades” in 5 was performed in the intermediate temperature region and also at coalescence. The lone pairs on the pnictogen atoms in 2–6 are oriented such that they form a bowl-shaped area that is somehow buried within the molecule.