Syntheses of novel di- and trinucleating ligands having a triethylbenzene core with N,N-bidentate tethers: their complexation toward Pd and Rh organometallic fragments
作者:Gou Higashihara、Akiko Inagaki、Munetaka Akita
DOI:10.1039/b713503c
日期:——
A series of di- and trinucleating ligands with a 1,3,5-triethylbenzene core connected to N,N-bidentate tethers was synthesized. The ligands readily reacted with monuclear Rh and Pd precursors to give the corresponding di- and trinuclear complexes, which were characterized by using NMR and ESI mass spectroscopy. In the solid state, the trinuclear complexes with ligands having pyridylpyrazolyl tethers adopt the most stable ababab configuration, in which the organometallic fragments are on the same side of the benzene plane. On the other hand, in solution, the linker moieties between the benzene core and the metals are flexible enough to interconvert between other configurations, that is, they exhibit dynamic behavior, and the rotational barrier was dependent on the length of the linkers. From variable temperature (VT) 1H NMR measurements, the rotational barrier for a trinuclear Rh–CO complex with a ligand having methylene linkers was estimated to be ∼12.6 kcal mol−1. However, no spectral changes were observed for the ethylene derivative in the temperature range of −60 °C to 50 °C, indicating that the rotation was not frozen out on the 1H NMR timescale, even at −60 °C.
我们合成了一系列以 1,3,5-三乙基苯为核心并与 N,N-二价拴连接的二核和三核配体。这些配体很容易与单核 Rh 和 Pd 前体发生反应,生成相应的二核和三核配合物,并通过核磁共振和 ESI 质谱对这些配合物进行了表征。在固态下,具有吡啶基吡唑三元组配体的三核配合物采用最稳定的 ababab 构型,其中的有机金属碎片位于苯平面的同一侧。另一方面,在溶液中,苯核心和金属之间的连接分子具有足够的灵活性,可以在其他构型之间相互转换,也就是说,它们表现出动态行为,旋转障碍取决于连接分子的长度。根据变温 (VT) 1H NMR 测量结果,含有亚甲基连接体的配体的三核 Rh-CO 复合物的旋转障碍估计为 ∼12.6 kcal mol-1。然而,在 -60 °C 至 50 °C 的温度范围内,乙烯衍生物的光谱没有发生变化,这表明即使在 -60 °C 时,旋转在 1H NMR 时间尺度上也没有冻结。