Dithiocarbamate Complexes of Ti(IV) Alkoxides: Synthesis, Characterization, and Electrochemistry

Isopropoxy- and tert-butoxy-tris(dithiocarbamato)titanium(IV) complexes of five dithiocarbamate ligands were prepared and characterized by LDI-MS, 1H NMR, 13C NMR, and elemental analysis, as well as by crystallographic determination of two examples. Both showed strongly π-coordinated alkoxy groups and two separate dithiocarbamate coordination environments that, in solution, were in rapid exchange. Cyclic voltammetry in CH2Cl2 revealed irreversible but reproducible oxidation peaks between +1.2 and +1.6 V vs Ag/AgCl, about 1 V positive of those from the free ligands, as well as reduction peaks in the −1.9 to −2.2 V range vs Ag/AgCl assigned to TiIV/III couples, and second reductions in some cases. The corresponding diisopropoxy-bis(dithiocarbamato) analogues were not isolable and slowly transformed to the more stable tris species. Indeed, these were shown to be in slow equilibrium.

本研究制备并表征了五种二硫代氨基甲酸酯配体的异丙氧基和叔丁氧基三(二硫代氨基甲酸酯)钛(IV)配合物，通过激光解吸电离质谱(LDI-MS)、1H核磁共振(NMR)、13C核磁共振(NMR)和元素分析进行，并通过对两个实例进行晶体结构测定。这些配合物均展现出强烈的π-配位的烷氧基团，以及两个独立的二硫代氨基甲酸酯配位环境，在溶液中处于快速交换状态。在CH2Cl2溶剂中的循环伏安法实验中，揭示了在+1.2至+1.6 V vs Ag/AgCl之间出现的不可逆但可重复的氧化峰，较游离配体的氧化峰约高1 V，以及-1.9至-2.2 V范围内的还原峰，对应于TiIV/III氧化还原对，某些情况下还存在第二次还原。相应的二异丙氧基双(二硫代氨基甲酸酯)类似物无法分离，并缓慢转化为更稳定的钛(IV)三配位物种。实际上，这些物种显示出缓慢的平衡状态。