Structural and Variable-Temperature NMR Studies of 9-Diisopropylphosphanylanthracenes and 9,10-Bis(diisopropylphosphanyl)anthracenes and Their Oxidation Products

The diisopropylphosphanyl-substituted anthracenes i-Pr2P(C14H9) (1a), i-Pr2P(C14H8)Br (2a), and (i-Pr2P)2(C14H8) (3a) and some of their oxidation products were prepared from 9-bromoanthracene and 9,10-dibromoanthracene, respectively. Low-temperature 1H NMR spectra of the 9-monophosphanyl-substituted anthracenes 1a and 2a are in accordance with a staggered conformer, while above room temperature dynamic processes occur. The low-temperature NMR spectrum of the 9,10-diphosphanylanthracene 3a indicates the presence of two different rotational isomers. The rotational barrier for 1a was determined from variable-temperature 1H NMR spectra to be 56 kJ mol−1 (ΔG298K). The crystal structure determinations show the solid-state conformers to be consistent with the prevailing conformer at low temperature.本研究分别以9-溴蒽和9,10-二溴蒽为原料，制备了二异丙基膦基取代蒽类化合物i-Pr₂P(C₁₄H₉)（1a）、i-Pr₂P(C₁₄H₈)Br（2a）、(i-Pr₂P)₂(C₁₄H₈)（3a）及其部分氧化产物。针对9-单膦基取代蒽1a和2a的低温氢核磁共振（¹H NMR）谱分析表明，其分子在低温下呈交错构象；当温度高于室温时，体系会发生动态分子过程。9,10-二膦基取代蒽3a的低温核磁共振谱显示存在两种不同的旋转异构体。通过变温氢核磁共振（¹H NMR）谱测定，1a的旋转势垒为56 kJ·mol⁻¹（ΔG₂₉₈K）。晶体结构测定结果显示，该类化合物在固态下的构象与低温下的优势构象一致。