Department of Chemistry, Kent State University, Kent, Ohio 44242, USA.
Dalton Trans. 2010 Feb 14;39(6):1616-9. doi: 10.1039/b914989a. Epub 2009 Dec 14.
Treatment of pink titanium(iii) triflate (0.045 M) with HF in triflic acid (CH(3)SO(3)H) converts Ti(iii) rapidly to a 1 : 1 mixture of Ti(IV) and green Ti(II): (2 Ti(III) + 4 HF --> TiF(4) + Ti(II) + 4 H(+)). This disproportionation is half complete when [HF] added is 0.027 M. Substituted 1,4-benzoquinones are reduced rapidly by Ti(iii) in the absence of fluoride, yielding straightforward logarithmic curves, but reactions of the same quinones with Ti(ii) in fluoride media exhibit more complex profiles, the major portions of which are zero order in oxidant. These reactions are strongly catalyzed by added Ti(iv). Analyses of complex curves are consistent with a reaction sequence initiated by Ti(ii)-Ti(iv) disproportionation, forming Ti(iii), which reacts with the quinone, yielding the quinhydrone, QH . The latter is rapidly reduced by Ti(ii). Values of rate constants obtained from these analyses are in agreement with those for reductions of quinones by Ti(iii), in the absence of fluoride.
用三氟甲磺酸（CH(3)SO(3)H）中的 HF 处理粉红色三氟甲磺酸钛(iii)（0.045 M）可将 Ti(iii)迅速转化为 Ti(IV)和绿色 Ti(II)的 1:1 混合物：(2 Ti(III) + 4 HF --> TiF(4) + Ti(II) + 4 H(+))。当添加的 HF 浓度为 0.027 M 时，歧化反应完成一半。在没有氟化物的情况下，取代的 1,4-苯醌被 Ti(iii)迅速还原，生成直接的对数曲线，但相同的苯醌与氟化物介质中的 Ti(ii)反应呈现出更复杂的曲线，其中大部分部分是以氧化剂为零级的。这些反应强烈地被添加的 Ti(iv)催化。对复杂曲线的分析与 Ti(ii)-Ti(iv)歧化反应引发的反应序列一致，形成 Ti(iii)，它与醌反应，生成醌氢醌，QH。后者被 Ti(ii)迅速还原。从这些分析中获得的速率常数值与没有氟化物时 Ti(iii)还原醌的速率常数值一致。
