Ye Heng-Yun, Dai Feng-Rong, Zhang Li-Yi, Chen Zhong-Ning
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, The Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Inorg Chem. 2007 Jul 23;46(15):6129-35. doi: 10.1021/ic0702771. Epub 2007 Jun 20.
Reaction of oxo-centered Ru(3)(III,III,III) precursor Ru(3)O(OAc)(6)(py)(2)(CH(3)OH) (1) with 1 equiv of 2,2'-azobispyridine (abpy) or 2,2'-azobis(5-chloropyrimidine) (abcp) induced the formation of stable Ru(3)(III,III,II) derivatives Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-L}(py)(2) (L = abpy (2), abcp (3)). As established in the structure of 3 by X-ray crystallography, 2 or 3 is derived from 1 by substitution of the axial methanol and one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core with abpy or abcp in an mu-eta(1)(N),eta(2)(N,N) bonding mode. Reduction of 3 by hydrazine induces isolation of one-electron reduced neutral Ru(3)(III,II,II) product Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-abcp}(py)(2) (3a). As revealed by electrochemical and spectroscopic studies, substituting one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core by abcp or abpy modifies dramatically the electronic and redox characteristics in the triruthenium derivatives. Relative to that for the parent compound Ru(3)O(OAc)(6)(py)(3) (E(1/2) = -0.46 V), triruthenium-based redox potential in the redox process Ru(3)O(III,III,III)/Ru(3)O(III,III,II) is significantly anodic-shifted to E(1/2) = +0.36 V for 2 and E(1/2) = +0.53 V for 3. Furthermore, the anodic shifts of redox potentials are progressively enhanced with a decrease of the formal oxidation states in the triruthenium cluster cores. As a consequence of remarkable positive shifts for redox potentials, the low-valence Ru(3)(III,III,II) and Ru(3)(III,II,II) species are stabilized and accessible.
以氧为中心的Ru(3)(III,III,III)前体Ru(3)O(OAc)(6)(py)(2)(CH(3)OH) (1)与1当量的2,2'-偶氮二吡啶(abpy)或2,2'-偶氮双(5-氯嘧啶)(abcp)反应，诱导形成稳定的Ru(3)(III,III,II)衍生物Ru(3)O(OAc)(5){μ-η(1)(N),η(2)(N,N)-L}(py)(2) (L = abpy (2), abcp (3))。通过X射线晶体学在3的结构中确定，2或3是由母体Ru(3)O(OAc)(6)簇核中的轴向甲醇和一个桥连乙酸盐被abpy或abcp以μ-η(1)(N),η(2)(N,N)键合模式取代而从1衍生而来。用肼还原3导致单电子还原的中性Ru(3)(III,II,II)产物Ru(3)O(OAc)(5){μ-η(1)(N),η(2)(N,N)-abcp}(py)(2) (3a)的分离。电化学和光谱研究表明，在母体Ru(3)O(OAc)(6)簇核中用abcp或abpy取代一个桥连乙酸盐会显著改变三钌衍生物的电子和氧化还原特性。相对于母体化合物Ru(3)O(OAc)(6)(py)(3) (E(1/2) = -0.46 V)，在氧化还原过程Ru(3)O(III,III,III)/Ru(3)O(III,III,II)中基于三钌的氧化还原电位显著正移至2的E(1/2) = +0.36 V和3的E(1/2) = +0.53 V。此外，氧化还原电位的正移随着三钌簇核中形式氧化态的降低而逐渐增强。由于氧化还原电位的显著正移，低价Ru(3)(III,III,II)和Ru(3)(III,II,II)物种得以稳定并可获得。
