Ariyarathna Isuru R, Miliordos Evangelos
Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, USA.
Phys Chem Chem Phys. 2021 Jan 21;23(2):1437-1442. doi: 10.1039/d0cp05513a.
Quantum chemical calculations are performed to study the S-H, O-H, and C-H bond activation of H2S, H2O, and CH4 by bare and ligated ZrO+ and NbO+ units. These representative oxides bear low energy oxo and higher energy oxyl units. S-H and C-H bonds are readily activated by metal oxyl states (radical mechanism), but the O-H bond is harder to activate with either the oxyl or oxo states. Our results suggest that known practices for the C-H bond activation can be applied to S-H, but not to O-H bonds. The identified trends are rationalized in terms of the HS-H, HO-H, and H3C-H dissociation energies to the homolytic or heterolytic fragments. We also found that these dissociation energies drop to about half after coordination of H2S or H2O to the metal oxide unit. In addition, chlorine ligands are shown to stabilize the higher energy oxyl states of the transition metal oxygen unit enhancing the reactivity of the formed complexes.
进行量子化学计算以研究裸露的和配位的ZrO⁺和NbO⁺单元对H₂S、H₂O和CH₄的S - H、O - H和C - H键的活化作用。这些具有代表性的氧化物含有低能量的氧代单元和较高能量的氧基单元。S - H键和C - H键容易被金属氧基态（自由基机理）活化，但O - H键无论是被氧基态还是氧代态活化都较为困难。我们的结果表明，已知的C - H键活化方法可应用于S - H键，但不适用于O - H键。根据HS - H、HO - H和H₃C - H到均裂或异裂碎片的解离能，对所确定的趋势进行了合理化解释。我们还发现，H₂S或H₂O与金属氧化物单元配位后，这些解离能下降到大约一半。此外，研究表明氯配体可稳定过渡金属氧单元的较高能量的氧基态，增强所形成配合物的反应活性。
