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Phenylene-Bridged Binuclear Organolanthanide Complexes as Catalysts for Intramolecular and Intermolecular Hydroamination

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posted on 27.04.2009 by Holming F. Yuen, Tobin J. Marks
The phenylene-bridged bimetallic organolanthanide complexes p-bis{Cp′′Ln[N(SiHMe2)2]2}phenylene (p-Ln2; Ln = Y, La, Cp′′ = tetramethylcyclopentadienyl) and m-bis{Cp′′La[N(SiHMe2)2]2}phenylene (m-La2) are investigated for possible Ln···Ln cooperative effects in hydroamination processes. These binuclear organolanthanide complexes efficiently catalyze the intramolecular hydroamination/cyclization of aminoalkenes, aminoalkynes, aminoallenes, and conjugated aminodienes with turnover frequencies as high as 10 h−1 at 60 °C, as well as intermolecular hydroaminations with turnover frequencies as high as 0.4 h−1 at 90 °C. Substrates include those having both compressed and extended junctures between the C−C unsaturation and the −NH2 group, as well as those with multiple −NH2 groups or places of C−C unsaturation. Reactivity trends appear to be dominated by nonbonded repulsive interactions, resulting in catalytic activities following the general trend m-Ln2 < p-Ln2. Organolanthanide amide complexes are also shown to catalyze the prototropic isomerization of alkynes.