title: N-Heterocyclic Carbene-Ytterbium Amide as a Recyclable Homogeneous Precatalyst for Hydrophosphination of Alkenes and Alkynes.
abstract: The N-heterocyclic carbene-ytterbium(II) amides (NHC)2Yb[N(SiMe3)2]2 (1: NHC: 1,3,4,5-tetramethylimidazo-2-ylidene (IMe4); 2: NHC: 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (IiPr)) and the NHC-stabilized rare-earth phosphide (IMe4)3Yb(PPh2)2 (3) have been synthesized and fully characterized. Complexes 1-3 are active precatalysts for the hydrophosphination of alkenes, alkynes, and dienes and exhibited much superior catalytic activity to that of the NHC-free amide (THF)2Yb[N(SiMe)2]2. Complex 1 is the most active precursor among the three complexes. In particular, complex 1 can be recycled and recovered from the reaction media after the catalytic reactions. Furthermore, it was found that complex 3 could catalyze the polymerization of styrene to yield atactic polystyrenes with low molecular weights. To the best of our knowledge, complex 1 represents the first rare-earth complex that can be recovered after catalytic reactions.
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P. R. China), Fax.
authors.forename: Jia
authors.initials: J
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P. R. China), Fax.
authors.forename: Hongfan
authors.initials: H
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P. R. China), Fax. cmcui@nankai.edu.cn.|Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300071, P. R. China. cmcui@nankai.edu.cn.
authors.forename: Chunming
authors.initials: C
authors.lastname: Cui
keywords: carbene ligands; homogeneous catalysis; hydrophosphination; nitrogen heterocycles; ytterbium