Cyclometalation of (2R,5R)-2,5-Diphenylpyrrolidine and 2-Phenyl-2-imidazoline Ligands with Half-Sandwich Iridium(III) and Rhodium(III) Complexes

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• 作者：Elias F茅ghali ; Laurent Barloy ; Jean-Thomas Issenhuth ; Lydia Karmazin-Brelot ; Corinne Bailly ; Michel Pfeffer
• 刊名：Organometallics
• 出版年：2013
• 出版时间：November 11, 2013
• 年：2013
• 卷：32
• 期：21
• 页码：6186-6194
• 全文大小：424K
• 年卷期：v.32,no.21(November 11, 2013)
• ISSN：1520-6041

文摘

Cyclometalation of (2R,5R)-2,5-diphenylpyrrolidine (1) with [(畏⁵-Cp*)MCl₂]₂ using NaOAc in CH₂Cl₂ at room temperature, followed by cationization with KPF₆ in CH₃CN, cleanly yielded the cationic cyclometalated amines 2a,b (a, M = Ir; b, M = Rh). This constituted an improvement with regard to another cyclometalation pathway, which had led to unwanted oxidation of the ligand to an imine. Compounds 2a,b were characterized by elemental analysis and X-ray diffraction of single crystals; the latter gave evidence of an R configuration of the metal center, and a 位 envelope conformation of the five-membered metallacycle. Successful application of the NaOAc/CH₂Cl₂ methodology to the cycloiridation and cyclorhodation of the imidazolines 3鈥?b>5 led to the neutral half-sandwich chloro complexes 6鈥?b>8, which were completely characterized, with yields ranging from 44% to 82%. In these complexes, the labile NH proton was localized in a 纬 position with regard to the metal. From the enantiopure chiral ligands 4 and 5, both diastereoisomers of the four compounds 7a,b and 8a,b were identified in solution by NMR; they were in equilibrium in solution. Complexes 6b, (S_M)-7a,b, and (R_M)-8a,b were characterized by radiocrystallography, which showed that the metallacycles were planar. Complexes 6鈥?b>8 were tested as catalysts for the reduction of acetophenone and imines by hydrogen transfer.