Synthesis, Characterization, and Reactivity of Ruthenium Hydride Complexes of N-Centered Triphosphine Ligands

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• 作者：Andreas Phanopoulos ; Neil J. Brown ; Andrew J. P. White ; Nicholas J. Long ; Philip W. Miller
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：April 7, 2014
• 年：2014
• 卷：53
• 期：7
• 页码：3742-3752
• 全文大小：500K
• 年卷期：v.53,no.7(April 7, 2014)
• ISSN：1520-510X

文摘

The reactivity of the novel tridentate phosphine ligand N(CH₂PCyp₂)₃ (N-triphos^Cyp, 2; Cyp = cyclopentyl) with various ruthenium complexes was investigated and compared that of to the less sterically bulky and less electron donating phenyl derivative N(CH₂PPh₂)₃ (N-triphos^Ph, 1). One of these complexes was subsequently investigated for reactivity toward levulinic acid, a potentially important biorenewable feedstock. Reaction of ligands 1 and 2 with the precursors [Ru(COD)(methylallyl)₂] (COD = 1,5-cycloocatadiene) and [RuH₂(PPh₃)₄] gave the tridentate coordination complexes [Ru(tmm){N(CH₂PR₂)₃-魏³P}] (R = Ph (3), Cyp (4); tmm = trimethylenemethane) and [RuH₂(PPh₃){N(CH₂PR₂)₃-魏³P}] (R = Ph (5), Cyp (6)), respectively. Ligands 1 and 2 displayed different reactivities with [Ru₃(CO)₁₂]. Ligand 1 gave the tridentate dicarbonyl complex [Ru(CO)₂{N(CH₂PPh₂)₃-魏³P}] (7), while 2 gave the bidentate, tricarbonyl [Ru(CO)₃{N(CH₂PCyp₂)₃-魏²P}] (8). This was attributed to the greater electron-donating characteristics of 2, requiring further stabilization on coordination to the electron-rich Ru(0) center by more CO ligands. Complex 7 was activated via oxidation using AgOTf and O₂, giving the Ru(II) complexes [Ru(CO)₂(OTf){N(CH₂PPh₂)₃-魏³P}](OTf) (9) and [Ru(CO₃)(CO){N(CH₂PPh₂)₃-魏³P}] (11), respectively. Hydrogenation of these complexes under hydrogen pressures of 3鈥?5 bar gave the monohydride and dihydride complexes [RuH(CO)₂{N(CH₂PPh₂)₃-魏³P}] (10) and [RuH₂(CO){N(CH₂PPh₂)₃-魏³P}] (12), respectively. Complex 12 was found to be unreactive toward levulinic acid (LA) unless activated by reaction with NH₄PF₆ in acetonitrile, forming [RuH(CO)(MeCN){N(CH₂PPh₂)₃-魏³P}](PF₆) (13), which reacted cleanly with LA to form [Ru(CO){N(CH₂PPh₂)₃-魏³P}{CH₃CO(CH₂)₂CO₂H-魏²O}](PF₆) (14). Complexes 3, 5, 7, 8, 11, and 12 were characterized by single-crystal X-ray crystallography.