Bridged bis(amidinate) lanthanide aryloxides: syntheses, structures, and catalytic activity for addition of amines to carbodiimides
作者:Jing Tu、Wenbo Li、Mingqiang Xue、Yong Zhang、Qi Shen
DOI:10.1039/c3dt33069a
日期:——
Various lanthanide aryloxide complexes supported by bridged bis(amidinate) ligand L, LLnOAr(DME) (L = Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3, DME = dimethoxyethane, Ln = Y, Ar = 2,6-(Me)2C6H3 (1), 2,6-(iPr)2C6H3 (2), 2,6-(tBu)2-4-(Me)C6H2 (3); Ar = 2,6-(tBu)2-4-(Me)C6H2, Ln = Nd (4), Sm (5), Yb (6)) were synthesized, and complexes 1, 2 and 4–6 were characterized by single crystal X-ray diffraction. All the complexes are efficient precatalysts for catalytic addition of amines to carbodiimides. The catalytic activity is influenced by lanthanide metals and the aryloxide groups (Nd (4) ∼ Sm (5) < Y (3) ∼ Yb (6) and -2,6-(Me)2C6H3 < -2,6-(iPr)2C6H3 < -2,6-(tBu)2-4-(Me)C6H2). The catalytic addition reaction with 3 showed a good scope of substrates. The mechanism investigation revealed the real active intermediate being the monoguanidinate complexes supported by an aryloxide and an amidine-functionalized amidinate group, L′Ln[O2,6-(tBu)2-4-(Me)C6H2][RNCNHRN(Ar′)] (L′ = Me3SiNHC(Ph)N(CH2)3NC(Ph)NSiMe3, R = iPr, Ar′ = phenyl, Ln = Yb (8), Y (11); R = Cy, Ar′ = phenyl, Ln = Yb (10), Y (12); R = iPr, Ar′ = 4-ClC6H4, Ln = Yb (9)), which were isolated from the reactions of 6 (or 3) with amine and carbodiimide in a molar ratio of 1 : 1 : 1 and structurally characterized. The Ln-active group in the present precatalyst is a Ln–amidinate species, not the Ln–OAr group.
合成了多种由桥接双氨基配体L支持的镧系元素芳氧化合物复合物LLnOAr(DME)(L = Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3,DME = 二甲氧基乙烷,Ln = Y,Ar = 2,6-(Me)2C6H3 (1),2,6-(iPr)2C6H3 (2),2,6-(tBu)2-4-(Me)C6H2 (3);Ar = 2,6-(tBu)2-4-(Me)C6H2,Ln = Nd (4),Sm (5),Yb (6)),并通过单晶X射线衍射对复合物1、2和4–6进行了表征。所有复合物都是催化胺与氨基二烯烃加成反应的有效前催化剂。催化活性受镧系金属和芳氧基团的影响(Nd (4) ∼ Sm (5) < Y (3) ∼ Yb (6) 和 -2,6-(Me)2C6H3 < -2,6-(iPr)2C6H3 < -2,6-(tBu)2-4-(Me)C6H2)。与3的催化加成反应显示了良好的底物范围。机制研究揭示了实际活性中间体是由芳氧基和氨基功能化的氨基配体组支持的单氨基化合物复合物L′Ln[O2,6-(tBu)2-4-(Me)C6H2][RNCNHRN(Ar′)](L′ = Me3SiNHC(Ph)N(CH2)3NC(Ph)NSiMe3,R = iPr,Ar′ = 苯基,Ln = Yb (8),Y (11);R = Cy,Ar′ = 苯基,Ln = Yb (10),Y (12);R = iPr,Ar′ = 4-ClC6H4,Ln = Yb (9)),这些复合物是通过6(或3)与胺和氨基二烯烃按1 : 1 : 1的摩尔比例反应而获得,并进行结构表征。本研究中的前催化剂中的Ln活性组分是Ln–氨基化物物种,而不是Ln–OAr基团。