The substitution reactions of the co-ordinated acetonitrile molecule in [NiL(MeCN)][BF4]2 1 (L = 2,5,8-trithia[9](2,9)-1,10-phenanthrolinophane) with different anionic and neutral ligands Lâ² [Clâ, Brâ, Iâ, CNâ, SCNâ, H2O, pyridine (py), aniline (an), 1,3-dimethyl-4-imidazoline-2-thione (etu) or 1,3-dimethyl-4-imidazoline-2-selone (eseu)] have been studied by using electronic spectroscopy. While the reaction with all the anionic ligands is quantitative, for the neutral ones an equilibrium takes place; the corresponding equilibrium constants have been determined in MeCN at 25 °C. The complex cations [NiL(Lâ²)](2 â n)+ (n = 0 for neutral and 1 for anionic ligands) have also been isolated in the solid state, mainly as BF4â salts and the compounds [NiL(H2O)][ClO4]2·H2O, [NiL(Cl)]Cl·H2O, [NiL(SCN)]BF4·MeNO2, [NiL(eseu)][BF4]2 and [NiL(py)][BF4]2 have been characterized by X-ray diffraction studies. In these complexes a distorted octahedral geometry is achieved at the NiII with five sites occupied by the macrocyclic ligand L and the sixth by the appropriate ligand Lâ². The electrochemistry of all the prepared compounds has been studied by cyclic voltammetry. In particular the reductive cyclic voltammetry of 1 in acetonitrile shows a quasi-reversible one-electron reduction wave near 1E½ = â1.0 V vs. Fc/Fc+. Electrochemical reduction by controlled-potential electrolysis at this potential in the presence of the axial ligand PMe3 and investigation of the reduced product by ESR spectroscopy confirm the reduction process to be metal based and to correspond to the formation of the [NiIL]+ species.
配位的
乙腈分子在 [NiL(MeCN)][ ]2 1(L = 2,5,8-三
硫[9](2,9)-1,10-
菲咯啉
酚)与不同阴离子和中性
配体 L' [Cl–, Br–, I–, CN–, SCN–,
H2O,
吡啶(py),
苯胺(an), 1,3-二甲基-4-
咪唑啉-2-
硫酮(etu)或 1,3-二甲基-4-
咪唑啉-2-
硒酮(eseu)] 的取代反应已被电子光谱学研究。所有阴离子
配体的反应都是定量的,而对于中性
配体则发生平衡;相应的平衡常数已在 MeCN 中 25 °C 下确定。配合阳离子 [NiL(L')](2–n)+(n = 0 中性
配体,n = 1 阴离子
配体)也在固态中分离,主要为
BF4– 盐,且化合物 [NiL( )][ClO4]2· 、[NiL(Cl)]Cl· 、[NiL(SCN)] ·MeNO2、[NiL(eseu)][ ]2 和 [NiL(py)][ ]2 已被 X 射线衍射研究表征。在这些配合物中,NiII 获得了一个扭曲的八面体几何结构,五个位点被大环
配体 L 占据,第六个位点被适当的
配体 L' 占据。所有制备的化合物已经通过循环伏安法研究了电
化学性质。特别是 1 在
乙腈中的还原循环伏安法显示出在 1E½ = –1.0 V(相对于 Fc/Fc+)附近的一个准可逆单电子还原波。在这个电位下的恒电位电解中的电
化学还原以及通过 ESR 光谱对还原产物的研究证实了还原过程是以
金属为基础的,并且对应于 [NiIL]+ 物种的形成。