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

Reaction of Ln(OAr1)3(THF)2 (Ar1= [2,6-(tBu)2-4-MeC6H2] with carbodiimides (RNCNR) in toluene afforded the RNCNR coordinated complexes (Ar1O)3Ln(NCNR) (R = iPr (isopropyl), Ln = Y (1) and Yb (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 (Ar1O)2Y[(4-Cl-C6H4N)C(NHiPr)NiPr](THF) (4) and (Ar1O)2Yb[(4-Cl-C6H4N)C(NHiPr)NiPr](THF) (5). Complexes 4 and 5 can be prepared by the reaction of Ln(OAr1)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(OAr2)3(THF)2 (Ar2 = [2,6-(iPr)2C6H3]) or Y(OAr3)3(THF)2 (Ar3 = [2,6-Me2C6H3]) did not occur. Complexes Ln(OAr1)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 complexes with the Ln-O active group. The catalytic activity of Y(OAr1)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 (Ar1O)2Ln[(2-OCH3-C6H4NH)(2-OCH3-C6H4NH2)] (6), was isolated by protonolysis of 4 with 2-OCH3-C6H4NH2. All the complexes were structurally characterized by X-ray single crystal determination.