β-Diketiminatoytterbium aryloxides: synthesis, structural characterization, and catalytic activity for addition of amines to carbodiimides

The steric effect of an aryloxido group on the synthesis and molecular structures of ytterbium aryloxides supported by -diketiminato ligand L (L=[N(2,6-Me2C6H3)C(Me)]2CH-) is reported. Reactions of -diketiminatoytterbium dichloride, LYbCl2(THF)2, with NaOAr1 in THF (Ar1=[2,6-tBu2-4-MeC6H2], THF=tetrahydrofuran) at 60 degrees C gave the corresponding ytterbium complexes LYb(OAr1)Cl(THF) () and LYb(OAr1)2 (1), depending on the molar ratio of dichloride to sodium aryloxide, respectively, while the same reactions with NaOAr2 and NaOAr3 (Ar2=[2,6-iPr2C6H3], Ar3=[2,6-Me2C6H3]) in 1:1 or 1:2 molar ratio in THF afforded only bisaryloxide complexes LYb(OAr2)2(THF) (1) and LYb(OAr3)2(THF) () in good yields, respectively. Complexes were fully characterized, including X-ray crystal structure analyses. All the complexes are efficient pre-catalysts for the catalytic addition of amines to carbodiimides giving guanidines. Copyright (c) 2013 John Wiley & Sons, Ltd.