Cangönül Asli, Behlendorf Maike, Gansäuer Andreas, van Gastel Maurice
Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
Inorg Chem. 2013 Oct 21;52(20):11859-66. doi: 10.1021/ic401403a. Epub 2013 Oct 10.
The binding of 2,2-diphenyloxirane to Cp2TiCl is studied on the electronic level by magnetic resonance spectroscopy and quantum chemical calculations. The complexation of 2,2-diphenyloxirane is accompanied by dissociation of the chloride ligand, and thus, the epoxide binds to the cationic titanocene(III) complex. The titanocene(III)-epoxide species persists only for short periods of time (<5 min) even at 243 K, indicating that the ring-opening reaction is exothermic. A short-lived paramagnetic titanocene(IV)-epoxide radical species has not been directly observed. However, by a combination of isotope labeling and spin-trapping, evidence for the existence of such a species has been unequivocally demonstrated. The observation of a titanocene(III)-epoxide complex is unprecedented and provides direct evidence for inner-sphere electron transfer between epoxides and titanocenes, responsible for the high regioselectivity of ring-opening.
通过磁共振光谱和量子化学计算在电子层面上研究了2,2-二苯基环氧乙烷与二氯二茂钛的结合。2,2-二苯基环氧乙烷的络合伴随着氯配体的解离，因此，环氧化物与阳离子二茂钛（III）络合物结合。即使在243 K下，二茂钛（III）-环氧化物物种也仅能持续很短的时间（<5分钟），这表明开环反应是放热的。尚未直接观察到短寿命的顺磁性二茂钛（IV）-环氧化物自由基物种。然而，通过同位素标记和自旋捕获相结合，已明确证明了这种物种的存在。二茂钛（III）-环氧化物络合物的观察是前所未有的，并为环氧化物和二茂钛之间的内球电子转移提供了直接证据，这是开环高区域选择性的原因。
