Reactions of fac(S)-[M(aet)3] (M = RhIII, IrIII; aet = 2-aminoethanethiolate) with an excess of VCl3 gave linear-type S-bridged trinuclear complexes [VIIIM(aet)3}2]3+ (M = RhIII
1, IrIII
2). The ΔΛ isomers (1a(ClO4)3 and 2a(ClO4)3) were selectively crystallized and their structures were determined by X-ray diffraction. Both the complex cations consist of two terminal fac(S)-[M(aet)3] units and a central vanadium atom, which is situated in an octahedral environment with a VIIIS6 chromophore. The Ir complex 2a was also formed by using VIVOCl2 instead of VIIICl3 in a redox reaction, whereas the Rh complex 1a was not formed by a similar method. The optically active isomer (ΛΛ-1b) of the Rh complex was selectively obtained by using Λ-fac(S)-[Rh(aet)3], and characterized by IR, UV-VIS absorption and CD spectra. All the obtained complexes exhibit a unique strong absorption band at ca. 18 × 103 cm−1. Stability and reactivity relating to V–S bond cleavage for the complexes were investigated using UV-VIS absorption spectroscopic methods. These studies show first order decomposition or metal exchange. While 2a has weaker V–S bonds than 1a (from the X-ray analyses), the former is considerably more stable in water than the latter. Cyclic voltammograms of 1a and 2a in water show only irreversible oxidation and reduction waves including VIV/III and VIII/II processes. The V(III) ions in the S-bridged trinuclear structures exhibit a lower magnetic moment (2.59 μB for 1a and 2.27 μB for 2a) at room temperature than the spin-only value for a d2 electronic configuration.
fac(S)-[M(aet)3](M = RhIII, IrIII; aet = 2-
氨基
乙硫醇)与过量的
VCl3反应,生成线性型S桥接三核络合物[VIIIM(aet)3}2]3+(M = RhIII 1,IrIII 2)。ΔΛ异构体(1a(
ClO4)3和2a( )3)被选择性结晶,并通过X射线衍射确定其结构。这两种络合物阳离子均由两个末端fac(S)-[M(aet)3]单元和一个位于八面体环境中的中心
钒原子组成,中心
钒原子的配位环境为VIIIS6色
氨酸。通过在氧化还原反应中用VIVOCl2代替VIIICl3,也可以形成
铱络合物2a,而
铑络合物1a则无法通过类似的方法形成。光学活性异构体(ΛΛ-1b)是通过使用Λ-fac(S)-[Rh(aet)3]选择性获得的,并通过红外光谱、紫外-可见吸收和圆二色谱进行表征。所有获得的络合物在约18 × 10^3 cm−1处表现出唯一的强吸收带。利用紫外-可见吸收光谱方法研究了这些络合物与V–S键断裂相关的稳定性和反应性。这些研究显示出一阶分解或
金属交换。虽然2a的V–S键比1a弱(根据X射线分析),但前者在
水中比后者稳定得多。1a和2a在
水中的循环伏安图仅显示出不可逆的氧化和还原波,包括VIV/III和VIII/II过程。在S桥接三核结构中的V(III)离子在室温下的磁矩(1a为2.59 μB,2a为2.27 μB)低于d2电子构型的自旋值。