Dinuclear Palladium(II) and -(III) Compounds with O,O-Chelating Ligands. Room-Temperature Direct 2-Phenylation of 1-Methylindole

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• 作者：Susana Ib谩帽ez ; Francisco Estevan ; Pipsa Hirva ; Mercedes Sana煤 ; M^a Angeles 脷beda
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8098-8108
• 全文大小：554K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

New dinuclear palladium(III) compounds of general formula Pd₂[(C₆H₄)PPh₂]₂[O鈥揙]₂Cl₂, O鈥揙 being chelating phenolates C₆H₄OC(O)R (R = CH₃, 3a; R = C₂H₅, 3b; R = OPh, 3c) or acetylacetonates RC(O)CHC(O)R (R = CH₃, 4a; R = CF₃, 4b; R = C(CH₃)₃, 4c), have been obtained by oxidation with PhICl₂ of the corresponding palladium(II) compounds. The stability of the new compounds has been studied by ³¹P NMR spectroscopy from 200 to 298 K. DFT calculations of the stability of the complexes have also been performed. In agreement with these calculations, only compound Pd₂[(C₆H₄)PPh₂]₂[(CF₃C(O)CHC(O)CF₃]₂Cl₂, 6b, showed the highest thermal stability. 6b was characterized by X-ray diffraction methods, presenting the longest Pd鈥揚d distance, 2,6403(6) 脜, observed among the already described discrete Pd₂⁶⁺compounds. The isolated palladium(II) and -(III) compounds have been tested at room temperature in the catalytic 2-phenylation of 1-methylindole with [Ph₂I]PF₆. With 3a as precatalyst the reaction was completed in 2 h with a 93% isolated yield. The results were compared with those obtained with other orthometalated dinuclear and mononuclear palladium compounds.