Synthesis and molecular structures of lanthanocene amide complexes and their catalytic activity for addition of amines to nitriles

Reaction of (CH3C5H4)2LnCl(THF) with NaNHAr in a 1:1 molar ratio in THF afforded the amide complexes (CH3C5H4)2LnNHAr(THF) [(Ar = 2,6-Me2C6H3, Ln = Yb (I), Y (III); Ar = 2,6-iPr2C6H3, Ln = Yb (II)]. X-ray crystal structure determination revealed that complexes I–III are isostructural. The central metal in each complex coordinated to two methylcyclopentadienyl groups, one amide group and one oxygen atom from THF to form a distorted tetrahedron. Complexes I–III and a known complex (CH3C5H4)2YbNiPr2(THF) IV all can serve as the catalysts for addition of amines to nitriles to monosubstituted N-arylamidines. The activity depended on the central metals and amide groups, and the active sequence follows the trend IV ≈ III < I < II.

Graphical abstractA series of lanthanide amide complexes stabilized by two methylcyclopentadienyl ligands were synthesized and well characterized. These lanthanocene amide complexes were found to serve as efficient catalysts for addition of amines to nitriles to give the monosubstituted N-arylamidines.Figure optionsDownload full-size imageDownload as PowerPoint slide