作者:Hisako Sato、Yukie Mori、Takafumi Kitazawa、Akihiko Yamagishi
DOI:10.1039/c2dt31746j
日期:——
Mononuclear and dinuclear ruthenium(III) complexes with bis-β-diketonato ligands (denoted by [Ru(acac)2(LâLH)] and [Ru(acac)2(LâL)Ru(acac)2], respectively) were synthesized, where acac, LâLHâ and LâL2â denote acetylacetonato, monoprotonated and unprotonated bis-β-diketonato ligands, respectively. The following three ligands were used as the bis-β-diketonato ligand (LâL2â): 1,2-diacetyl-1,2-dibenzoylethanato (denoted by dabe2â), 1,2-diacetyl-1,2-bis(3-methylbutanoyl)ethanato (baet2â) and 1,2-diacetyl-1,2-dipropanoylethanato (dpe2â). For the mononuclear and the meso-type dinuclear complexes, a pair of diastereomeric species were identified as Î- (or Î-) [Ru(acac)2(R- or S-LâLH)] and [Î-Ru(acac)2(R- or S-LâL)Î-Ru(acac)2], respectively. The possibility of thermal inversion in coordinated LâLHâ (mononuclear) or LâL2â (dinuclear) was pursued by monitoring the changes in the electronic circular dichroism or the 1H NMR spectra. No inversion occurred for the dinuclear complexes, when their chloroform solutions were kept at 50 °C for ca. 100 h. In contrast, some of the mononuclear complexes underwent the inversion of axial chirality to give an equilibrium mixture under the same conditions. The reaction followed the first-order rate law and the overall first-order rate constants (k) of [Ru(acac)2(LâLH)] were determined to be k = 0.13, 0.0048 and less than 0.001 hâ1 for LâLHâ = dabeHâ, baetHâ and dpeHâ, respectively. The results suggest that the main factor determining the barrier height of the internal rotation is not the steric but the electronic properties of the carbonâcarbon bond connecting the two β-diketonato moieties.
合成了带有双δ-二酮配体(分别用[Ru(acac)2(LâLH)]和[Ru(acac)2(LâL)Ru(acac)2]表示)的单核和双核钌(III)配合物,其中 acac、LâLHâ 和 LâL2â 分别表示乙酰丙酮配体、单质子化配体和非质子化双δ-二酮配体。以下三种配体被用作双δ-二酮配体(LâL2â):1,2-二乙酰基-1,2-二苯甲酰乙烷配体(dabe2â)、1,2-二乙酰基-1,2-双(3-甲基丁酰基)乙烷配体(baet2â)和 1,2-二乙酰基-1,2-二丙酰乙烷配体(dpe2â)。对于单核和介型双核配合物,一对非对映异构体分别被鉴定为δ-(或δ-)[Ru(acac)2(R-或 S-LâLH)]和[δ-Ru(acac)2(R-或 S-LâL)δ-Ru(acac)2]。通过监测电子圆二色性或 1H NMR 光谱的变化,研究了配位 LâLHâ(单核)或 LâL2â(双核)热反转的可能性。当双核复合物的氯仿溶液在 50 ° C 下保持约 100 小时时,不会发生反转。相反,在相同条件下,一些单核络合物发生了轴向手性反转,生成了平衡混合物。反应遵循一阶速率定律,在 LâLHâ = dabeHâ, baetHâ 和 dpeHâ 时,[Ru(acac)2(LâLH)] 的总一阶速率常数 (k) 分别为 k = 0.13, 0.0048 和小于 0.001 hâ1 。结果表明,决定内旋转障碍高度的主要因素不是连接两个 δ-二酮分子的碳碳键的立体性质,而是其电子性质。