Synthesis, Characterization, Selective Catalytic Activity, and Reactivity of Rare Earth Metal Amides with Different Metal−Nitrogen Bonds

• Published in: Organometallics 2009-07, Vol.28 (13), p.3882-3888
• Main Authors: Zhu, Xiancui, Fan, Jiaxi, Wu, Yunjun, Wang, Shaowu, Zhang, Lijun, Yang, Gaosheng, Wei, Yun, Yin, Chengwei, Zhu, Hong, Wu, Shihong, Zhang, Hongtao
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om900191j

A series of neutral rare earth metal amides with different metal−nitrogen bonds were synthesized and characterized. The selective catalytic activity and reactivity of the complexes incorporating different metal−nitrogen (Ln−N, Ln = rare earth metal) bonds were studied. Treatment of (Me2Si)[(2,6-R1 2-4-R2-C6H2)NH]2 with [(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 in toluene produced the neutral rare earth metal complexes {(Me2Si)[(2,6-R1 2-4-R2-C6H2)N]2}LnN(SiMe3)2(THF) (R1 = i Pr, R2 = H, Ln = Yb (1), Y (2), Eu (3), Sm (4), Nd (5); R1 = R2 = H, Ln = Yb (6), Sm (7)) incorporating different Ln−N bonds in good yields. Reaction of 6 or 7 with grease (Me2SiO)3 in toluene produced the selective insertion products [C6H5N(Me2Si)N(C6H5)(Me2SiO)LnN(SiMe3)2]2 (Ln = Yb (8), Sm (9)). The structures of complexes 1, 2, 4, 5, 8, and 9 were additionally determined by single-crystal X-ray analyses. Investigation of catalytic activity of the complexes indicated that the complexes displayed a high selectivity on cyclotrimerization or cyclodimerization toward isocyanates depending on the nature of the isocyanates. These catalysts have the advantages of a high reactivity and good selectivity toward isocyanates, easy preparation, low catalyst loading, and high conversion, as well as mild reaction conditions.