کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1300723 1498837 2006 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Kinetic studies of the photoinduced formation of transition metal-dinitrogen complexes using time-resolved infrared and UV-vis spectroscopy
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
Kinetic studies of the photoinduced formation of transition metal-dinitrogen complexes using time-resolved infrared and UV-vis spectroscopy
چکیده انگلیسی
Previous kinetic studies of photoinitiated transition metal-dinitrogen bond forming reactions are reviewed, with an emphasis on room temperature reactivity, and in particular, the techniques of time-resolved infrared (TRIR) spectroscopy and UV-vis flash photolysis. Our recent results on the reactivity of the formally 16-electron, but agostically stabilized, complex, mer,trans-W(CO)3(PCy3)2 (W) (Cy = cyclohexyl) toward N2 in toluene and n-hexane solution are then discussed. Laser flash photolysis of a toluene solution of W-N2 in the presence of excess N2 resulted in the photoejection of N2. The back reaction of W with N2 was followed by monitoring the decay of the transient absorption of W at 600 nm. The second-order rate constant for the reaction of N2 with W in toluene to generate W-N2 was found to be (3.0 ± 0.2) × 105 M−1 s−1. The rate of the reverse reaction was found to be 100 ± 10 s−1, allowing an estimation of the equilibrium constant, KN2=(3.0±0.5)×103M−1. Time-resolved step-scan FTIR (s2-FTIR) spectroscopy was also used to spectroscopically characterize the W intermediate and monitor its back-reaction with N2 in n-hexane solution. The rate of formation of W-N2 measured by s2-FTIR agreed well with that measured by flash photolysis. Finally, density functional theory (DFT) calculations have been performed on the model complexes, mer,trans-W(CO)3(PH3)2(L) (L = none and N2) in order to understand the observed IR and UV-vis spectra of W and W-N2 and to determine the nature of the frontier molecular orbitals of W and W-N2, allowing their lowest energy excited states to be assigned.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Coordination Chemistry Reviews - Volume 250, Issues 13–14, July 2006, Pages 1681-1695
نویسندگان
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