Competing Pathways in the Photochemistry of Ru(H) 2 (CO)(PPh 3 ) 3
Competing Pathways in the Photochemistry of Ru(H) 2 (CO)(PPh 3 ) 3
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Ru(H) 2 (CO)(PPh 3 ) 3 光化学中的竞争途径
DOI：
10.1021/acs.organomet.7b00802
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发表时间：
2018
期刊：
影响因子：
2.8
通讯作者：
Procacci B
中科院分区：
文献类型：
--
作者：
Procacci B
利用激光和常规光源，结合核磁共振和红外光谱，重新研究了Ru(H)_2(CO)(PPh_3)_3(1)的光化学。利用p-H2诱导极化(PhIP)提高了核磁共振实验的灵敏度，观察到了一系列意想不到的反应。(A)通过在p-H_2存在下脉冲激光光解的超极化观察，以及(B)通过对瞬时[Ru(CO)(PPh_3)_3]的纳秒时间分辨红外光谱研究，证明了H_2的光诱导还原消除。消除H_2与光诱导的PPh_3的损失竞争，如核磁共振光谱检测到的二氢、三苯基砷和吡啶取代产物的形成所证明的那样。根据TRIR光谱，相应的配位不饱和16电子中间体[Ru(H)2(CO)(PPh3)2]以两种异构体形式存在，分别与H_2和吡啶在纳秒时间尺度上反应。这两条途径，即还原消除H_2和P_Ph_3损失，在355 nm辐射下以大致相同的量子产率发生。在H_2存在下的低温光解反应生成了二氢络合物Ru(H)_2(η_2-H_2)(CO)(PPh_3)_2。这种络合物在室温下几秒钟内就会进一步反应，它的行为为解释PhIP结果提供了理论基础。此外，在AsPh_3和H_2存在下的光解生成Ru(H)_2(AsPh_3)(CO)(PPh_3)_2。根据在H_2存在下吡啶的初始光解的核磁共振光谱，得到了Ru(H)_2(CO)(PPh_3)_2(吡啶)的两个异构体。另外还有两个异构体作为次要产物形成；每个异构体的构型都通过核磁共振光谱进行了鉴定。用激光泵浦-核磁共振探测光谱观察了吡啶配合物的一个异构体的磁化强度的相干振荡，振荡频率对应于氢化物共振之间的化学位移的差异。并用三次红外光谱检测了吡啶取代产物。
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 ofp-H2-induced polarization (PHIP), and a series of unexpected reactions were observed. The photoinduced reductive elimination of H2was demonstrated (a) via NMR spectroscopy by the observation of hyperpolarized1on pulsed laser photolysis in the presence ofp-H2and (b) via nanosecond time-resolved infrared (TRIR) spectroscopy studies of the transient [Ru(CO)(PPh3)3]. Elimination of H2competes 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 H2and with pyridine on a nanosecond time scale. These two pathways, reductive elimination of H2and PPh3loss, are shown to occur with approximately equal quantum yields upon 355 nm irradiation. Low-temperature photolysis in the presence of H2reveals 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 AsPh3and H2generates 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 of1in 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.