Activation of carbodiimide and transformation with amine to guanidinate group by Ln(OAr)_3(THF)_2 (Ln: Lanthanide and yttrium) and Ln(OAr)_3(THF)_2 as a novel precatalyst for addition of amines to carbodiimides: Influence of aryloxide group

摘要

Reaction of Ln(OAr~1)_3(THF)_2 (Ar ~1= [2,6-(tBu)2- 4-MeC_6H_2] with carbodiimides (RNCNR) in toluene afforded the RNCNR coordinated complexes (Ar ~1O)_3Ln(NCNR) (R = iPr (isopropyl), Ln = Y (1) andYb (2); R = Cy (cyclohexyl), Ln = Y (3)) in high yields. Treatment of 1 and 2 with 4-chloroaniline, respectively, at a molar ratio of 1:1 yielded the corresponding monoguanidinate complex (Ar~1O)2Y[(4-Cl-C6H4N)C(NHiPr) N ~iPr](THF) (4) and (Ar~1O)_2Yb[(4-Cl-C _6H_4N)C(NH~iPr)N~iPr] (THF) (5). Complexes 4 and 5 can be prepared by the reaction of Ln(OAr~1)3(THF)2 with RNCNR and amine in toluene at a 1:1:1 molar ratio in high yield directly. A remarkable influence of the aryloxide ligand on this transformation was observed. The similar transformation using the less bulky yttrium complexes Y(OAr~2)3(THF)2 (Ar~2 = [2,6-(i Pr)2C6H3]) or Y(OAr _2)_3(THF)_2 (Ar~3 = [2,6- Me _2C_6H_3]) did not occur. Complexes Ln(OAr ~1)3(THF)2 were found to be the novel precatalysts for addition of RNCNR with amines, which represents the first example of catalytic guanylation by the lanthanide complexeswith the Ln-O active group.The catalytic activity of Y(OAr~1)3(THF)_2 was found to be the same as that of monoguanidinate complex 4, indicating 4 is one of the active intermediates in the present process. The other intermediate, amide complex (Ar ~1O)_2Ln[(2-OCH_3-C_6H _4NH)(2-OCH3-C6H4NH2)] (6), was isolated by protonolysis of 4 with 2-OCH_3-C_6H_4NH_2. All the complexes were structurally characterized by X-ray single crystal determination.