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 β‐diketiminato ligand L (L = [N(2,6‐Me 2 C 6 H 3 )C(Me)] 2 CH − ) is reported. Reactions of β‐diketiminatoytterbium dichloride, LYbCl 2 (THF) 2 , with NaOAr 1 in THF (Ar 1  = [2,6‐ t Bu 2 ‐4‐MeC 6 H 2 ], THF = tetrahydrofuran) at 60°C gave the corresponding ytterbium complexes LYb(OAr 1 )Cl(THF) ( 1 ) and LYb(OAr 1 ) 2 (1), depending on the molar ratio of dichloride to sodium aryloxide, respectively, while the same reactions with NaOAr 2 and NaOAr 3 (Ar 2  = [2,6‐ i Pr 2 C 6 H 3 ], Ar 3  = [2,6‐Me 2 C 6 H 3 ]) in 1:1 or 1:2 molar ratio in THF afforded only bisaryloxide complexes LYb(OAr 2 ) 2 (THF) (1) and LYb(OAr 3 ) 2 (THF) ( 4 ) in good yields, respectively. Complexes 1 , 2 , 3 , 4 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 © 2013 John Wiley & Sons, Ltd.