The photochemistry of Ru(H)₂(CO)(PPh₃)₃ (1) has been reinvestigated employing laser and conventional light sources in conjunction with NMR spectroscopy and IR spectroscopy. The sensitivity of NMR experiments was enhanced by use of p-H₂-induced polarization (PHIP), and a series of unexpected reactions were observed. The photoinduced reductive elimination of H₂ was demonstrated (a) via NMR spectroscopy by the observation of hyperpolarized 1 on pulsed laser photolysis in the presence of p-H₂ and (b) via nanosecond time-resolved infrared (TRIR) spectroscopy studies of the transient [Ru(CO)(PPh₃)₃]. Elimination of H₂ competes with photoinduced loss of PPh₃, as demonstrated by formation of dihydrogen, triphenylarsine, and pyridine substitution products which are detected by NMR spectroscopy. The corresponding coordinatively unsaturated 16-electron intermediate [Ru(H)₂(CO)(PPh₃)₂] exists in two isomeric forms according to TRIR spectroscopy that react with H₂ and with pyridine on a nanosecond time scale. These two pathways, reductive elimination of H₂ and PPh₃ loss, are shown to occur with approximately equal quantum yields upon 355 nm irradiation. Low-temperature photolysis in the presence of H₂ reveals the formation of the dihydrogen complex Ru(H)₂(η²-H₂)(CO)(PPh₃)₂, which is detected by NMR and IR spectroscopy. This complex reacts further within seconds at room temperature, and its behavior provides a rationale to explain the PHIP results. Furthermore, photolysis in the presence of AsPh₃ and H₂ generates Ru(H)₂(AsPh₃)(CO)(PPh₃)₂. Two isomers of Ru(H)₂(CO)(PPh₃)₂(pyridine) are formed according to NMR spectroscopy on initial photolysis of 1 in the presence of pyridine under H₂. Two further isomers are formed as minor products; the configuration of each isomer was identified by NMR spectroscopy. Laser pump-NMR probe spectroscopy was used to observe coherent oscillations in the magnetization of one of the isomers of the pyridine complex; the oscillation frequency corresponds to the difference in chemical shift between the hydride resonances. Pyridine substitution products were also detected by TRIR spectroscopy.

中文翻译：

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Ru（H）₂（CO）（PPh ₃）₃的光化学竞争途径

Ru（H）₂（CO）（PPh ₃）₃（1）的光化学已经重新研究，采用激光和常规光源结合NMR光谱学和IR光谱学。通过使用p -H ₂诱导的极化（PHIP）增强了NMR实验的灵敏度，并观察到一系列意外反应。（a）通过NMR光谱通过在p -H ₂存在下脉冲激光光解中超极化1的观察证明了H ₂的光诱导还原消除。（b）通过纳秒时间分辨红外（TRIR）光谱研究瞬态[Ru（CO）（PPh ₃）₃ ]。H _2的消除与PPh _3的光诱导损失竞争，正如通过NMR光谱检测到的二氢，三苯ar和吡啶取代产物的形成所证明的。根据TRIR光谱学，相应的配位不饱和的16电子中间体[Ru（H）₂（CO）（PPh ₃）₂ ]以两种异构体形式存在，它们以纳秒级与H ₂和吡啶反应。这两个途径，还原消除H ₂和PPh ₃结果表明，在355 nm辐射下，光子的损耗以近似相等的量子产率发生。在H存在的低温光解₂揭示了复杂的二氢茹（H）的形成₂（η ² -H ₂）（CO）（PPH ₃）₂，以NMR和IR光谱检测。该复合物在室温下可在数秒内进一步反应，其行为为解释PHIP结果提供了理论依据。此外，在AsPh ₃和H ₂的存在下光解产生Ru（H）₂（AsPh ₃）（CO）（PPh ₃）₂。Ru（H）_2的两个异构体（CO）（PPh ₃）₂（吡啶）是根据NMR光谱在H ₂下在吡啶存在下对1进行初始光解而形成的。作为次要产物，形成了另外两种异构体。通过NMR光谱法鉴定每种异构体的构型。使用激光泵浦-NMR探针光谱法观察吡啶配合物的一种异构体在磁化过程中的相干振荡。振荡频率对应于氢化物共振之间化学位移的差异。吡啶取代产物也通过TRIR光谱法检测。