Distinctive structural features of hydroxyamino-1,3,5-triazine ligands leading to enhanced hydrolytic stability of their titanium complexes
作者:Dani Peri、Jacob S. Alexander、Edit Y. Tshuva、Artem Melman
DOI:10.1039/b606072b
日期:——
Three bis(homoleptic) titanium complexes of hydroxyamino-1,3,5-triazine ligands 3a–c were synthesized and characterized, and their kinetic behavior in THF–water solutions was studied at various pH conditions using UV-vis, based on the characteristic Ti–O band at 380 nm. One of these complexes, 3c, was analyzed by X-ray crystallography. Due to the characteristic electronic structure of the triazine rings, high electron density on the nitrogen atoms leads to strong N–Ti bonds, as indicative by the 2.0 Å coordinative bond lengths in the X-ray structure. Consequently, these complexes exhibit high hydrolytic stability over a wide pH range, where hydrolysis was observed to be promoted by basic conditions. At neutral pH, t1/2 was estimated to be >200 h, whereas at pH = 5.5, no hydrolysis was observed for a period of at least three days.
合成并表征了羟基氨基-1,3,5-三嗪配体 3a-c 的三种双(同色)钛络合物,并根据 380 纳米波长处的特征钛-O 带,利用紫外可见光谱研究了它们在不同 pH 值条件下在 THF-水溶液中的动力学行为。对其中一个复合物 3c 进行了 X 射线晶体学分析。由于三嗪环的特征电子结构,氮原子上的高电子密度导致了很强的 N-Ti 键,X 射线结构中 2.0 Å 的配位键长度就说明了这一点。因此,这些复合物在很宽的 pH 值范围内都表现出很高的水解稳定性。在中性 pH 值条件下,t1/2 估计大于 200 小时,而在 pH = 5.5 条件下,至少在三天内没有观察到水解现象。