The series of compounds W2(μ-E)(μ-OCH2tBu)2(OCH2tBu)6, where E = O, S, Se, or Te, has been isolated from the reactions between [W2(OCH2tBu)8]n and pyridine N-oxide, elemental sulfur, elemental selenium and tri-n-butylphosphine telluride. The reactions were carried out in hexane or toluene solutions, and the new compounds were isolated as crystalline products by recrystallization from hexanes at low temperatures (E = O, S, Se) or from hot toluene (E = Te). Each compound displays temperature-dependent 1H NMR spectra indicative of bridge â terminal alkoxide group exchange which is frozen out at ca.
â65 °C. The low-temperature spectra are consistent with the observed molecular structures in the solid
state as determined by single-crystal X-ray studies. There is a central O3M(μ-O)2(μ-E)MO3 skeleton having virtual C2ν symmetry. The WâW internuclear distances range from 2.55 to 2.66 Ã
and gradually increase along the series O â S â Se â Te. The compounds are colored (E = O: violet; E = S: blue; E = Se: blue-green; and E = Te: dark yellow/amber) as a result of absorptions in the visible region of the spectrum. The electronic structures of these compounds have been investigated using density functional theory (DFT) by examining the model compounds W2(μ-E)(μ-OCH3)2(OCH3)6 (E = O, S, Se, or Te). These B3LYP(SDD,6-31G*) calculations reveal that the HOMO is a MâM Ï-type molecular orbital,
and with increasing mass of E, the orbital energies of the EpÏ lone-pair orbitals approach this level. A tentative assignment of the electronic absorption spectra is made on the basis of time-dependent DFT (TDDFT) calculations.
从 [W2(OCH2tBu)8]n 和N-氧化
吡啶、元素
硫、元素
硒和三正丁基
碲化膦。反应在己烷或
甲苯溶液中进行,通过低温己烷(E = O、S、Se)或热
甲苯(E = Te)重结晶,将新化合物分离为结晶产物。每种化合物都显示出与温度相关的 1H NMR 谱,表明桥与末端醇盐基团的交换,该交换在约 100°C 时被冻结。
≤65°C。低温光谱与观察到的固体分子结构一致
由单晶 X 射线研究确定的状态。有一个中心 O3M(μ-O)2(μ-E)MO3 骨架,具有虚拟 C2μ 对称性。 W-W 核间距范围为 2.55 至 2.66 ×,并沿 O - S - Se - Te 序列逐渐增大。这些化合物由于可见光区域的吸收而呈现颜色(E = O:紫色;E = S:蓝色;E = Se:蓝绿色;E = Te:深黄色/琥珀色)光谱。通过检查模型化合物 W2(μ-E)(μ-OCH3)2(OCH3)6 (E = O、S、Se 或 Te),使用密度泛函理论 (DFT) 研究了这些化合物的电子结构。这些 B3LYP(
SDD,6-31G*) 计算表明 HOMO 是 M–M Ï 型分子轨道,
随着E质量的增加,EpÏ孤对轨道的轨道能量接近这个
水平。电子吸收光谱的初步分配是基于时间相关的 DFT (TDDFT) 计算。