Ruthenium(II) Arene Complexes with Asymmetrical Guanidinate Ligands: Synthesis, Characterization, and Application in the Base-Free Catalytic Isomerization of Allylic Alcohols

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• 作者：Roc铆o Garcı ; ́ ; a-脕lvarez ; Francisco J. Su谩rez ; Josefina Dı ; ́ ; ez ; Pascale Crochet ; Victorio Cadierno ; Antonio Anti帽olo ; Rafael Fern谩ndez-Gal谩n ; Fernando Carrillo-Hermosilla
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8301-8311
• 全文大小：442K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

The ruthenium(II) arene dimer [{RuCl(渭-Cl)(畏⁶-p-cymene)}₂] readily reacted with 4 equiv of guanidines (ⁱPrHN)₂C鈺怤R (R = ⁱPr (1a), 4-C₆H₄^tBu (1b), 4-C₆H₄Br (1c), 2,4,6-C₆H₂Me₃ (1d), 2,6-C₆H₃ⁱPr₂ (1e)) in toluene at room temperature to generate the mononuclear complexes [RuCl{魏²N,N鈥?C(NR)(NⁱPr)NHⁱPr}(畏⁶-p-cymene)] (2a鈥?b>e) and the easily separable guanidinium chloride salts [(ⁱPrHN)₂C(NHR)][Cl] (3a鈥?b>e). Compounds 2a鈥?b>e and 3a鈥?b>e were fully characterized by elemental analysis and IR and NMR spectroscopy. The structures of [RuCl{魏²N,N鈥?C(NⁱPr)₂NHⁱPr}(畏⁶-p-cymene)] (2a) and [RuCl{魏²N,N鈥?C(N-4-C₆H₄^tBu)(NⁱPr)NHⁱPr}(畏⁶-p-cymene)] (2b) were also determined by X-ray diffraction analysis. Regardless of the steric requirements of the aromatic substituents, a nonsymmetric coordination of the guanidinate anions in 2b鈥?b>e was observed, in complete accord with theoretical calculations (DFT) on the corresponding [RuCl{魏²N,N鈥?C(NR)(NⁱPr)-NHⁱPr}(畏⁶-p-cymene)] and [RuCl{魏²N,N鈥?C(NⁱPr)₂NHR}(畏⁶-p-cymene)] models. Remarkably, complexes 2a鈥?b>e were active catalysts for the redox isomerization of allylic alcohols in the absence of base, which represents the first catalytic application known for ruthenium guanidinate species.