Experimental and Computational Evidence for the Participation of Nonclassical Dihydrogen Species in Proton Transfer Processes on Ru鈥揂rene Complexes with Uncoordinated N Centers. Efficient Catalytic De

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• 作者：Gustavo Espino ; Agust铆n Caballero ; Blanca R. Manzano ; Luc铆a Santos ; Mercedes P茅rez-Manrique ; Miquel Moreno ; F茅lix A. Jal贸n
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 23, 2012
• 年：2012
• 卷：31
• 期：8
• 页码：3087-3100
• 全文大小：567K
• 年卷期：v.31,no.8(April 23, 2012)
• ISSN：1520-6041

文摘

The protonation with Br酶nsted acids HB (HBF₄ and CF₃CO₂H) of [RuH₂(arene)(PPh₂Het)] derivatives (PPh₂Het = dpim, Het = 2-N-methylimidazolyl; PPh₂Het = PPh₂py, Het = 2-pyridyl) that contain uncoordinated N atoms has been analyzed experimentally by NMR spectroscopy and through computational studies. Initially, at low temperature, the uncoordinated N atoms of the phosphine are protonated and a proton鈥揾ydride exchange is observed by ¹H NMR spectroscopy. The proton transfer leads to the corresponding cationic trihydride intermediates, which exhibit a dual character of classical and nonclassical hydrides, with the nonclassical species being more stable, especially when Het = 2-pyridyl. In fact, the release of H₂ and the formation of the respective monohydride complexes [RuH(arene)(魏²-N,P-PPh₂Het)]B was observed at room temperature. The participation of the uncoordinated N center in the proton transfer process in the stabilization of RuH(H₂)⁺ with respect to RuH₃⁺ species and in the hydride鈥揹ihydrogen exchange (cis effect) are discussed. Calculations on the complex [RuH₃(p-cymene)(PPh₃)]⁺ have also been carried out for the sake of comparison. A dual character was also found, but in this case the classical species is more stable. H/D exchange of the hydride ligands of the dihydride complexes, using CD₃OD as the deuterium source, has been studied. The very rapid deuterium labeling of H₂, catalyzed by the aforementioned dihydrides, has been observed. The known compound [RuH₂(p-cymene)(PPh₃)] is also active in this labeling process, and the possible mechanism for both the H/D exchange and the deuterium labeling of H₂ is discussed in light of theoretical studies.