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Divalent Heteroleptic Ytterbium Complexes – Effective Catalysts for Intermolecular Styrene Hydrophosphination and Hydroamination

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posted on 03.02.2014, 00:00 by Ivan V. Basalov, Sorin Claudiu Roşca, Dmitry M. Lyubov, Alexander N. Selikhov, Georgy K. Fukin, Yann Sarazin, Jean-François Carpentier, Alexander A. Trifonov
New heteroleptic Yb­(II)–amide species supported by amidinate and 1,3,6,8-tetra-tert-butylcarbazol-9-yl ligands [2-MeOC6H4NC­(tBu)­N­(C6H3-iPr2-2,6)]­YbN­(SiMe3)2(THF) (6) and [1,3,6,8-tBu4C12H4N]­Yb­[N­(SiMe3)2]­(THF)n (n = 1 (7), 2 (8)) were synthesized using the amine elimination approach. Complex 6 features an unusual κ1-N2-O6-arene coordination mode of the amidinate ligand onto Yb­(II). Complexes 7 and 8 represent the first examples of lanthanide complexes with π-coordination of carbazol-9-yl ligands. Complexes 6 and 7, as well as the amidinate–Yb­(II)–amide [tBuC­(NC6H3-iPr2-2,6)2]­YbN­(SiMe3)2(THF) (5), are efficient precatalysts for the intermolecular hydrophosphination and hydroamination of styrene with diphenylphosphine, phenylphosphine, and pyrrolidine to give exclusively the anti-Markovnikov monoaddition product. For both types of reaction, the best performances were observed with carbazol-9-yl complex 7 (TONs up to 92 and 48 mol/mol at 60 °C, respectively).