Divalent first-row transition metal complexes of the rigid pendant-arm ligand 1,4,7-tris(2-aminophenyl)-1,4,7-triazacyclononane †
作者:Ian A. Fallis、Richard D. Farley、K. M. Abdul Malik、Damien M. Murphy、Hayley J. Smith
DOI:10.1039/b005402j
日期:——
The rigid pendant-arm macrocyclic ligand 1,4,7-tris(2-aminophenyl)-1,4,7-triazacyclononane (L1) has been synthesized. It reacts with divalent first row transition metal perchlorate salts to yield complexes of general formula [MII(L1)][ClO4]2 (M = FeII, NiII, CuII or ZnII). Single crystal X-ray crystallography indicated that [FeII(L1)][ClO4]2 and [NiII(L1)][ClO4]2 are isostructural with both complex cations consisting of distorted pseudo-octahedral six-co-ordinate metal centres with three macrocyclic N-donors and three anilino donors. The mean Fe–N bond length in [FeII(L1)][ClO4]2 was found to be 2.10 Å, which is intermediate between the normal ranges of high and low spin FeIIN6 species. Magnetometry and EPR measurements indicated that single crystals of [FeII(L1)][ClO4]2 were predominately low spin, with approximately 5% of a low spin iron(III) species present in the lattice. It is postulated that this latter species is the mono anilido complex [FeIII(L1−H)][ClO4]2. The crystal structure of [NiII(L1)][ClO4]2 indicated a short mean Ni–N bond length of 2.09 Å. The ligand field strength for this material was found to have a very high value of 12,330 cm−1 (B = 850 cm−1) and is compared to that of some related trigonal NiIIN6 species. The crystal structure of [CuII(L1)][ClO4]2 was also determined and indicated a distorted six-co-ordinate metal centre. The X-band EPR spectrum of this complex in magnetically dilute solid solution indicated a predominantly axial species, although a slight rhombic distortion may be present. The variable temperature 1H NMR of [ZnII(L1)][ClO4]2 in CD3CN solution revealed a non-fluxional six-co-ordinate complex. Electrochemical analyses of the complexes indicated only irreversible oxidation and reduction processes for [NiII(L1)][ClO4]2 and [CuII(L1)][ClO4]2. [FeII(L1)][ClO4]2 displays at least two reversible oxidation processes with the first at +0.181 V (vs. Fc–Fc+) being assigned as a metal centred FeII → FeIII process and the second at +0.475 V as a ligand centred process.
我们合成了刚性垂臂大环配体 1,4,7-三(2-氨基苯基)-1,4,7-三氮杂环壬烷(L1)。它与二价第一排过渡金属高氯酸盐反应,生成通式为 [MII(L1)][ClO4]2 (M = FeII、NiII、CuII 或 ZnII)的配合物。单晶 X 射线晶体学显示,[FeII(L1)][ClO4]2 和 [NiII(L1)][ClO4]2 具有同构结构,这两种配合物的阳离子都由扭曲的假八面体六配位金属中心与三个大环 N 供体和三个苯胺供体组成。研究发现,[FeII(L1)][ClO4]2 中的平均 Fe-N 键长度为 2.10 Å,介于高自旋和低自旋 FeIIN6 物种的正常范围之间。磁力测量和 EPR 测量表明,[FeII(L1)][ClO4]2 的单晶体主要是低自旋的,晶格中约有 5% 的低自旋铁(III)物种。据推测,后者是单苯胺络合物 [FeIII(L1-H)][ClO4]2。镍II(L1)][ClO4]2的晶体结构表明其平均镍-镍键长度较短,为 2.09 Å。该材料的配体场强值非常高,为 12,330 cm-1 (B = 850 cm-1),与一些相关的三方镍铟络合物(NiIIN6)的配体场强值相近。此外,还测定了 [CuII(L1)][ClO4]2的晶体结构,结果表明它具有一个扭曲的六配位金属中心。该复合物在磁稀释固溶体中的 X 波段 EPR 光谱显示,虽然可能存在轻微的菱形畸变,但主要是轴向物种。在 CD3CN 溶液中,[ZnII(L1)][ClO4]2 的变温 1H NMR 显示出一种非氟化物的六配位复合物。复合物的电化学分析表明,[NiII(L1)][ClO4]2 和 [CuII(L1)][ClO4]2只有不可逆的氧化和还原过程。[FeII(L1)][ClO4]2至少有两个可逆的氧化过程,第一个在 +0.181 V 处(相对于 Fc-Fc+)是以金属为中心的 FeII → FeIII 过程,第二个在 +0.475 V 处是以配体为中心的过程。