Misochko Eugenii Ya, Akimov Alexander V, Belov Vasilii A, Tyurin Daniil A
Institute of Problems of Chemical Physics of the Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russia.
Inorg Chem. 2009 Sep 21;48(18):8723-8. doi: 10.1021/ic9007312.
Xenon trifluoride radicals were generated by the solid-state chemical reaction of mobile fluorine atoms with XeF(2) molecules isolated in a solid argon matrix. On the basis of spectroscopic and kinetic FTIR measurements and performed quantum chemical calculations, two infrared absorption bands at 568 (strong) and 523 (very weak) cm(-1) have been assigned to asymmetric and symmetric Xe-F stretching vibrational modes of radical ()XeF(3), respectively. Chemical reaction of fluorine atom with XeF(2) in a solid argon cage obeys specific kinetic behavior indicating the formation of a long-lived intermediate complex under the condition that the diffusing fluorine atom is attached to isolated XeF(2) at temperatures 20 K < T < 27 K. Subsequent thermally activated conversion in the complex is the main source of novel xenon-containing radical species (*)XeF(3). The rate constant and energy barrier are estimated for the reaction in an argon cage, [XeF(2)-F] --> (K(r)) [XeF(3)], as K(r) approximately 7 x 10(-5) c(-1) at 27 K and E approximately 1.2 kcal/mol, respectively. Quantum chemistry calculations reveal that radical ()XeF(3) has a planar C(2v) structure. DFT calculations show that formation of the third Xe-F bond in the (*)XeF(3) radical is exothermic, and the binding energy of the third Xe-F bond is 8-20 kcal/mol.
三氟化氙自由基是通过固态化学反应产生的，即移动的氟原子与隔离在固态氩基质中的XeF₂分子发生反应。基于光谱学和动力学傅里叶变换红外光谱测量以及进行的量子化学计算，在568 cm⁻¹（强）和523 cm⁻¹（非常弱）处的两个红外吸收带分别被归属为自由基XeF₃的不对称和对称Xe - F伸缩振动模式。在固态氩笼中，氟原子与XeF₂的化学反应遵循特定的动力学行为，这表明在20 K < T < 27 K的温度条件下，当扩散的氟原子附着到隔离的XeF₂上时，会形成一种长寿命的中间络合物。随后该络合物中的热激活转化是新型含氙自由基物种XeF₃的主要来源。对于氩笼中的反应[XeF₂ - F] → (K(r)) [XeF₃]，估计其速率常数和能垒分别为在27 K时K(r)约为7×10⁻⁵ c⁻¹，E约为1.2 kcal/mol。量子化学计算表明自由基XeF₃具有平面C₂ᵥ结构。密度泛函理论计算表明，在XeF₃自由基中形成第三个Xe - F键是放热的，且第三个Xe - F键的结合能为8 - 20 kcal/mol。
